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  • 1.
    Beyer, Jan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Suraprapapich, S
    Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, USA .
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Hyperfine-induced spin depolarization and dynamic nuclear polarization in InAs/GaAs quantum dots2012Conference paper (Other academic)
  • 2.
    Beyer, Jan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Suraprapapich, S.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California 92093, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Temperature dependence of dynamic nuclear polarization and its effect on electron spin relaxation and dephasing in InAs/GaAs quantum dots2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 14, p. 143105-Article in journal (Refereed)
    Abstract [en]

    Electron spin dephasing and relaxation due to hyperfine interaction with nuclear spins is studied in an InAs/GaAs quantum dot ensemble as a function of temperature up to 85 K, in an applied longitudinal magnetic field. The extent of hyperfineinduced dephasing is found to decrease, whereas dynamic nuclear polarization increases with increasing temperature. We attribute both effects to an accelerating electron spin relaxation through phonon-assisted electron-nuclear spin flip-flops driven by hyperfine interactions, which could become the dominating contribution to electron spin depolarization at high temperatures.

  • 3.
    Beyer, Jan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, P. H.
    Suraprapapich, S.
    Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, USA .
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Spin properties in InAs/GaAs quantum dot structures: Invited talk at the Second Int. Conf. on Small Science (ICSS 2012), Orlando, USA, Dec.16-19 2012.2012Conference paper (Other academic)
  • 4.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Wang, X. J.
    Tu, C. W.
    University of California, La Jolla, California, United States.
    Ptak, Aaron J.
    National Renewable Energy Lab, Golden, Colorado, United States.
    Geelhaar, L.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    How to Deactivate Harmful Defects and Active them for New Spin Functionalities in a Semiconductor?2015In: Abstract Book, 2015, p. FF3.02-Conference paper (Refereed)
    Abstract [en]

    We demonstrate a general approach via spin engineering that is capable of not only deactivating defect-mediated efficient non-radiative carrier recombination channels in a semiconductor that are harmful to photonic and photovoltaic device performance, but also adding new room-temperature (RT) spin functionalities that are desirable for future spintronics and spin-photonics but so far unachievable otherwise. This approach exploits the Pauli Exclusion Principle that prohibits occupation of a non-degenerate defect level by two spin-parallel electrons, thereby providing spin blockade of carrier recombination via the defect level. The success of the approach is demonstrated in the dilute nitride of Ga(In)NAs, which holds promises for low-cost, highly efficient lasers for fiber-optic communications as well as for multi-band and multi-junction solar cell applications. First we identify that Gai self-interstitials and their complexes are the most common grown-in defects found in Ga(In)NAs grown by both molecular beam epitaxy (MBE) and metalorganic chemical vapour deposition (MOCVD). They provide a dominant non-radiative shunt path for non-equilibrium carriers, leading to low efficiencies of light-emitting and photon-charge carrier conversion. Spin blockade is shown to lead to a giant enhancement by up to 800% in light emission intensity at RT.Furthermore we show that via spin engineering these seemingly harmful defects can be turned into advantages by adding unconventional defect-enabled spin functionalities that are highly effective at RT, including some of the fundamental building blocks essential for future spintronics. We demonstrate efficient defect-engineered spin filtering in Ga(In)NAs, which is capable of generating a record-high degree (> 40%) of electron spin polarization at RT [Nature Materials 8, 198 (2009), Phys. Rev. B 89, 195412 (2014)]. We also provide the first experimental demonstration of an efficient RT spin amplifier based on defect engineered Ga(In)NAs with a spin gain up to 2700% [Adv. Materials 25, 738 (2013)]. Such a spin amplifier is shown to be capable of amplifying a fast-modulating input spin signal while truthfully maintaining its time variation of the spin-encoded information [7]. By taking advantage of the spin amplification effect, we show that Ga(In)NAs can be employed as efficient RT spin detectors, with spin detection efficiency well exceeding 100% [8,9]. By combining the spin-filtering effect and hyperfine coupling, we further achieve the first realization of RT nuclear spin hyperpolarization in semiconductors via conduction electrons [Nature Communications. 4, 1751 (2013)], relevant to nuclear spin qubits. We believe that such defect-enabled spin functionalities could potentially provide an attractive, alternative solution to the current and important issues on RT spin injection, spin amplification and spin detection in semiconductors for future spintronics.

  • 5.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, X. J.
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China .
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Extraordinary Room-Temperature Spin Functionality In A Non-Magnetic Semiconductor2013Conference paper (Other academic)
  • 6.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, X. J.
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China .
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Ptak, Aaron J.
    National Renewable Energy Laboratory, Golden, Colorado, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Geelhaar, L.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Ga interstitials: usual grown-in defects with unusual room-temperature spin functionality in dilute nitrides2013Conference paper (Other academic)
  • 7.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, X. J.
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China .
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Ptak, A. J.
    National Renewable Energy Laboratory, Golden, Colorado, USA.
    Geelhaar, Lutz
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Spin functional non-magnetic semiconductors for future spintronics2013Conference paper (Other academic)
  • 8.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, X. J.
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China .
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Ptak, A. J.
    National Renewable Energy Laboratory, Golden, Colorado.
    Geelhaar, Lutz
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, Henning
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Exploring room-temperature spin functionality in non-magnetic semiconductor nanostructures.: Invited talk at the 5th IEEE International Nanoelectronics Conference (IEEE INEC 2013), Singapore, Jan.2-4, 2013.2013Conference paper (Other academic)
  • 9.
    Dagnelund, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Yonezu, H.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Japan .
    Ptak, A. J.
    National Renewable Energy Laboratory, Golden, Colorado, USA.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Effects of substrate defects on photoluminescence of GaNP and GaNAs epitaxial layers: optically detected magnetic resonance study2012Conference paper (Other academic)
  • 10.
    Filippov, Stanislav
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Huang, Yuqing
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Suraprapapich, Suwaree
    Department of Electrical and Computer Engineering, University of California, La Jolla, California, United States.
    Tu, Charles. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California 92093, United States.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Exciton Fine-Structure Splitting in Self-Assembled Lateral InAs/GaAs Quantum-Dot Molecular Structures2015In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 6, p. 5741-5749Article in journal (Refereed)
    Abstract [en]

    Fine-structure splitting (FSS) of excitons in semiconductor nanostructures is a key parameter that has significant implications in photon entanglement and polarization conversion between electron spins and photons, relevant to quantum information technology and spintronics. Here, we investigate exciton FSS in self-organized lateral InAs/GaAs quantum-dot molecular structures (QMSs) including laterally aligned double quantum dots (DQDs), quantum-dot clusters (QCs), and quantum rings (QRs), by employing polarization-resolved microphotoluminescence (μPL) spectroscopy. We find a clear trend in FSS between the studied QMSs depending on their geometric arrangements, from a large FSS in the DQDs to a smaller FSS in the QCs and QRs. This trend is accompanied by a corresponding difference in the optical polarization directions of the excitons between these QMSs, namely, the bright-exciton lines are linearly polarized preferably along or perpendicular to the [11̅0] crystallographic axis in the DQDs that also defines the alignment direction of the two constituting QDs, whereas in the QCs and QRs, the polarization directions are randomly oriented. We attribute the observed trend in the FSS to a significant reduction of the asymmetry in the lateral confinement potential of the excitons in the QRs and QCs as compared with the DQDs, as a result of a compensation between the effects of lateral shape anisotropy and piezoelectric field. Our work demonstrates that FSS strongly depends on the geometric arrangements of the QMSs, which effectively tune the degree of the compensation effects and are capable of reducing FSS even in a strained QD system to a limit similar to strain-free QDs. This approach provides a pathway in obtaining high-symmetry quantum emitters desirable for realizing photon entanglement and spintronic devices based on such nanostructures, utilizing an uninterrupted epitaxial growth procedure without special requirements for lattice-matched materials combinations, specific substrate orientations, and nanolithography.

  • 11.
    Fillipov, Stanislav
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Huang, Yuqing
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Suraprapapich, Suwaree
    Department of Electrical and Computer Engineering, University of California, La Jolla, California, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California, USA.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Control of exciton fine-structure splitting in geometrically engineered self-assembled InAs/GaAs quantum molecular structuresManuscript (preprint) (Other academic)
    Abstract [en]

    Fine-structure splitting (FSS) of excitons in semiconductor nanostructures is a key parameter that has significant implications in photon entanglement and polarization conversion between electron spins and photons, relevant to quantum information technology and spintronics. Here, we investigate exciton FSS in self-organized InAs/GaAs quantum molecular structures (QMSs) including laterally-aligned double quantum dots (DQDs), quantum-dot clusters (QCs) and quantum rings (QRs), by employing polarization-resolved micro-photoluminescence spectroscopy. We find a clear trend in FSS between the studied QMSs depending on their geometric arrangements, from a large FSS in the DQDs to a smaller FSS in the QCs and QRs with an overall higher geometric symmetry. This trend is accompanied by a corresponding difference in the optical polarization directions of the excitons between these QMSs, namely, the bright-exciton lines are linearly polarized preferably along or perpendicular to the [11̅0] crystallographic axis in the DQDs that also defines the alignment of the two constituting QDs, whereas in the QCs and QRs the polarization directions are randomly oriented. We attribute the observed trends in the FSS to a significant reduction of the anisotropic strain field in the high symmetry QCRs and QCs as compared with the low-symmetry  DQDs. Our work demonstrates that FSS can be effectively controlled by geometric engineering of the QMSs, capable of reducing FSS even in a strained QD system to a limit similar to strain-free QDs. This approach provides a new pathway in obtaining high-symmetry quantum emitters desirable for realizing photon entanglement and spintronic devices based on such nanostructures, without special requirements for lattice-matched materials combinations, specific substrate orientations and nanolithography.

  • 12.
    Guo, Yiting
    et al.
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Liu, Yanfeng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zhu, Qinglian
    Xi An Jiao Tong Univ, Peoples R China.
    Li, Cheng
    Chinese Acad Sci, Peoples R China.
    Jin, Yingzhi
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Liu, Feng
    Hebei Univ, Peoples R China.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ma, Wei
    Xi An Jiao Tong Univ, Peoples R China.
    Li, Weiwei
    Chinese Acad Sci, Peoples R China.
    Effect of Side Groups on the Photovoltaic Performance Based on Porphyrin-Perylene Bisimide Electron Acceptors2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 38, p. 32454-32461Article in journal (Refereed)
    Abstract [en]

    In this work, we developed four porphyrin-based small molecular electron acceptors for non-fullerene organic solar cells, in which different side groups attached to the porphyrin core were selected in order to achieve optimized performance. The molecules contain porphyrin as the core, perylene bisimides as end groups, and the ethynyl unit as the linker. Four side groups, from 2,6-di(dodecyloxy)phenyl to (2-ethylhexyl)thiophen-2-yl, pentadecan-7-yl, and 3,5-di(dodecyloxy)phenyl unit, were applied into the electron acceptors. The new molecules exhibit broad absorption spectra from 300 to 900 nm and high molar extinction coefficients. The molecules as electron acceptors were applied into organic solar cells, showing increased power conversion efficiencies from 1.84 to 5.34%. We employed several techniques, including photoluminescence spectra, electroluminescence spectra, atomic force microscopy, and grazing-incidence wide-angle X-ray to probe the blends to find the effects of the side groups on the photovoltaic properties. We found that the electron acceptors with 2,6-di(dodecyloxy)phenyl units show high-lying frontier energy levels, good crystalline properties, and low nonradiative recombination loss, resulting in possible large phase separation and low energy loss, which is responsible for the low performance. Our results provide a detailed study about the side groups of non-fullerene materials, demonstrating that porphyrin can be used to design electron acceptors toward near-infrared absorption.

  • 13.
    Huang, Yuqing
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Spin injection and detection in semiconductor nanostructures (invited talk)2016In: 7TH IEEE INTERNATIONAL NANOELECTRONICS CONFERENCE (INEC) 2016, IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    We review our recent results from optical spin orientation studies of In(Ga)As/GaAs quantum dots (QD) and QD molecular structures (QMSs), which shed light on some critical issues in spin injection and spin detection in these semiconductor nanostructures.

  • 14.
    Huang, Yuqing
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Spin injection loss in self-assembled InAs/GaAs quantum dot structures from disordered barrier layers2016In: 2016 IEEE 16TH INTERNATIONAL CONFERENCE ON NANOTECHNOLOGY (IEEE-NANO), IEEE , 2016, p. 627-629Conference paper (Refereed)
    Abstract [en]

    Semiconductor quantum dot (QD) structures are considered as promising building block for spintronic applications with the advantage of prolonged spin relaxation time owing to 0D character of confined carriers or excitons. However, feasible application is haunted by severe spin injection loss from its adjacent barrier layers and its mechanism is still not fully understood. Here, we show that exciton spin injection in self-assembled InAs/GaAs QD molecular structures (QMSs) is dominated by localized excitons confined within the QD-like regions of the wetting layer (WL) and GaAs barrier layer surrounding QD structures. The origin of spin injection loss is attribute to finite anisotropic exchange interaction (AEI) of the localized excitons subjected to asymmetric confinement potential in the injection layers. As a result, the AEI of the injected excitons and, thus, the spin injection efficiency is determined to be correlated with the overall geometric symmetry of QMSs, which hold strong influence on the confinement potential of the localized excitons in the surrounding barrier layers. Our results shed light on the microscopic origin of the spin injection loss in QD structures. More importantly, they offer a useful guideline to significantly improve spin injection efficiency by optimizing the lateral arrangement of QMSs and overcome a major challenge in the QD based spintronic device applications.

  • 15.
    Huang, Yuqing
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Yang, X. J.
    Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan.
    Subagyo, A.
    Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan.
    Sueoka, K.
    Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan.
    Murayama, A.
    Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Size dependence of electron spin dephasing in InGaAs quantum dots2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 106, no 9, p. 093109-Article in journal (Refereed)
    Abstract [en]

    We investigate ensemble electron spin dephasing in self-assembled InGaAs/GaAs quantum dots (QDs) of different lateral sizes by employing optical Hanle measurements. Using low excitation power, we are able to obtain a spin dephasing time T-2* (in the order of ns) of the resident electron after recombination of negative trions in the QDs. We show that T-2* is determined by the hyperfine field arising from the frozen fluctuation of nuclear spins, which scales with the size of QDs following the Merkulov-Efros-Rosen model. This scaling no longer holds in large QDs, most likely due to a breakdown in the lateral electron confinement. (C) 2015 AIP Publishing LLC.

  • 16.
    Huang, Yuqing Q.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Understanding and optimizing spin injection in self-assembled InAs/GaAs quantum-dot molecular structures2016In: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 9, no 3, p. 602-611Article in journal (Refereed)
    Abstract [en]

    Semiconductor quantum-dot (QD) structures are promising for spintronic applications owing to strong quenching of spin relaxation processes promoted by carrier and excitons motions. Unfortunately, spin injection efficiency in such nanostructures remains very low and the exact physical mechanism for the spin loss is still not fully understood. Here, we show that exciton spin injection in self-assembled InAs/GaAs QDs and quantum-dot molecular structures (QMSs) is dominated by localized excitons confined within the QD-like regions of the wetting layer (WL) and GaAs barrier layer immediately surrounding QDs and QMSs that in fact lack the commonly believed 2D and 3D character with an extended wavefunction. We identify the microscopic origin of the observed severe spin loss during spin injection as being due to a sizable anisotropic exchange interaction (AEI) of the localized excitons in the WL and GaAs barrier layer, which has so far been overlooked. We find that the AEI of the injected excitons and thus the efficiency of the spin injection processes are correlated with the overall geometric symmetry of the QMSs, as the latter largely defines the anisotropy of the confinement potential of the localized excitons in the surrounding WL and GaAs barrier. These results pave the way for a better understanding of spin injection processes and the microscopic origin of spin loss in QD structures, which in turn provides a useful guideline to significantly improve spin injection efficiency by optimizing the lateral arrangement of the QMSs thereby overcoming a major bottleneck in spintronic device applications utilizing semiconductor QDs.

  • 17.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Room-temperature defect-engineered spin functionalities in Ga(In)NAs alloys2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Semiconductor spintronics is one of the most interesting research fields that exploits both charge and spin properties for future photonics and electronic devices. Among many challenges of using spin in semiconductors, efficient generation of electron spin polarization at room temperature (RT) remains difficult. Recently, a new approach using defect-mediated spin filtering effect, employing -interstitial defects in Ga(In)NAs alloys, has been shown to turn the material into an efficient spin-polarized source capable of generating >40% conduction electron spin polarization at RT without an application of external fields. In order to fully explore the defectengineered spin functionalities, a better understanding and control of the spin filtering effects is required. This thesis work thus aims to advance our understanding, in terms of both physical and material insights, of the recently discovered spin filtering defects in Ga(In)NAs alloys. We have focused on the important issues of optimization and applications of the spin filtering effects.

    To improve spin filtering efficiency, important material and defect parameters must be addressed. Therefore, in Papers I–III formation of the  defects in Ga(In)NAs alloys has been examined under different growth and post-growth treatment conditions, as well as in different structures. We found that the  defects were the dominant and important nonradiative recombination centers in Ga(In)NAs epilayers and GaNAs/GaAs multiple quantum wells, independent of growth conditions and post-growth annealing. However, by varying growth and post-growth conditions, up to four configurations of the  defects, exhibiting different hyperfine  interaction (HFI) strengths between defect electron and nuclear (e-n) spins, have been found. This difference was attributed to different interstitial sites and/or complexes of  . Further studiesfocused on the effect of post-growth hydrogen (H) irradiation on the spin filtering effect. Beside the roles of H passivation of N resulting in bandgap reopening of the alloys, H treatment was shown to lead to complete quenching of the spin filtering effect, accompanied by strong suppression in the concentrations of the  defects. We concluded that the observed effect was due to the passivation of the  defects by H, most probably due to the formation of H- complexes.

    Optimizing spin filtering efficiency also requires detailed knowledge of spin interactions at the defect centers. This issue was addressed in Papers IV and V. From both experimental and theoretical studies, we were able to conclude that the HFI between e-n spins at the  defects led to e-n spin mixing, which degraded spin filtering efficiency at zero field.  Moreover, we have identified the microscopic origin of electron spin relaxation (T1) at the defect centers, that is, hyperfine-induced e-n spin cross-relaxation. Our finding thus provided a guideline to improve spin filtering efficiency by selectively incorporating the  defects with weak HFI by optimizing growth and post-growth treatment conditions, or by searching for new spin filtering defect centers containing zero nuclear spin.

    The implementation of the defect-engineered spin filtering effect has been addressed in Papers VI–VIII. First, we experimentally demonstrated for the first time at RT an efficient electron spin amplifier employing the  defects in Ga(In)NAs alloys, capable of amplifying a weak spin signal up to 27 times with a high cut-off frequency of 1 GHz. We further showed that the defectmediated spin amplification effect could turn the GaNAs alloy into an efficient RT optical spin detector. This enabled us to reliably conduct in-depth spin injection studies across a semiconductor heterointerface at RT. We found a strong reduction of electron spin polarization after optical spin injection from a GaAs layer into an adjacent GaNAs layer. This observation was attributed to severe spin loss across the heterointerface due to structural inversion asymmetry and probably also interfacial point defects.

    Finally, we went beyond the generation of strongly polarized electron spins. In Paper IX we focused on an interesting aspect of using strongly polarized electron spins to induce strong nuclear spin polarization at RT, relevant to solid-state quantum computation using a defect nuclear spin of long spin memory as a quantum bit (qubit). By combining the spin filtering effect and the HFI, we obtained a sizeable nuclear spin polarization of ~15% at RT that could be sensed by conduction electrons. This demonstrated the feasibility of controlling defect nuclear spins via conduction electrons even at RT, the first case ever being demonstrated in a semiconductor.

    List of papers
    1. Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials
    Open this publication in new window or tab >>Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials
    Show others...
    2009 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, p. 241904-Article in journal (Refereed) Published
    Abstract [en]

    Opticallydetected magnetic resonance measurements are carried out to study formationof Ga interstitial-related defects in Ga(In)NAs alloys. The defects, whichare among dominant nonradiative recombination centers that control carrier lifetimein Ga(In)NAs, are unambiguously proven to be common grown-in defectsin these alloys independent of the employed growth methods. Thedefects formation is suggested to become thermodynamically favorable because ofthe presence of nitrogen, possibly due to local strain compensation.

    Place, publisher, year, edition, pages
    American Institute of Physics, 2009
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-52858 (URN)10.1063/1.3275703 (DOI)
    Note
    Original Publication: Xingjun Wang, Yuttapoom Puttisong, C. W. Tu, Aaron J. Ptak, V. K. Kalevich, A. Yu. Egorov, L. Geelhaar, H. Riechert, Weimin Chen and Irina Buyanova, Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials, 2009, Applied Physics Letters, (95), 241904. http://dx.doi.org/10.1063/1.3275703 Copyright: American Institute of Physics http://www.aip.org/Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2017-12-12Bibliographically approved
    2. Electron spin filtering by thin GaNAs/GaAs multiquantum wells
    Open this publication in new window or tab >>Electron spin filtering by thin GaNAs/GaAs multiquantum wells
    Show others...
    2010 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 5, p. 052104-Article in journal (Refereed) Published
    Abstract [en]

    Effectiveness of the recently discovered defect-engineered spin-filtering effect is closely examined in GaNAs/GaAs multiquantum wells (QWs) as a function of QW width. In spite of narrow well widths of 3-9 nm, rather efficient spin filtering is achieved at room temperature. It leads to electron spin polarization larger than 18% and an increase in photoluminescence intensity by 65% in the 9 nm wide QWs. A weaker spin filtering effect is observed in the narrower QWs, mainly due to a reduced sheet concentration of spin-filtering defects (e.g., Ga-i interstitial defects).

    Keywords
    electron spin polarisation, gallium arsenide, III-V semiconductors, nitrogen compounds, photoluminescence, semiconductor quantum wells
    National Category
    Engineering and Technology Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-54084 (URN)10.1063/1.3299015 (DOI)000274319500045 ()
    Available from: 2010-02-22 Created: 2010-02-22 Last updated: 2017-12-12Bibliographically approved
    3. Room temperature spin filtering effect in GaNAs: Role of hydrogen
    Open this publication in new window or tab >>Room temperature spin filtering effect in GaNAs: Role of hydrogen
    Show others...
    2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 15, p. 152109-Article in journal (Refereed) Published
    Abstract [en]

    Effects of hydrogen on the recently discovered defect-engineered spin filtering in GaNAs are investigated by optical spin orientation and optically detected magnetic resonance. Post-growth hydrogen treatments are shown to lead to nearly complete quenching of the room-temperature spin-filtering effect in both GaNAs epilayers and GaNAs/GaAs multiple quantum wells, accompanied by a reduction in concentrations of Ga(i) interstitial defects. Our finding provides strong evidence for efficient hydrogen passivation of these spin-filtering defects, likely via formation of complexes between Gai defects and hydrogen, as being responsible for the Observed strong suppression of the spin-filtering effect after the hydrogen treatments.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2011
    Keywords
    gallium arsenide, gallium compounds, hydrogen, III-V semiconductors, interstitials, magnetic resonance, passivation, quenching (thermal), semiconductor epitaxial layers, semiconductor quantum wells, wide band gap semiconductors
    National Category
    Engineering and Technology Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-72139 (URN)10.1063/1.3651761 (DOI)000295883800045 ()
    Available from: 2011-11-18 Created: 2011-11-18 Last updated: 2017-12-08Bibliographically approved
    4. Effect of hyperfine-induced spin mixing on the defect-enabled spin blockade and spin filtering in GaNAs
    Open this publication in new window or tab >>Effect of hyperfine-induced spin mixing on the defect-enabled spin blockade and spin filtering in GaNAs
    2013 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 12Article in journal (Refereed) Published
    Abstract [en]

    The effect of hyperfine interaction (HFI) on the recently discovered room-temperature defect-enabled spin-filtering effect in GaNAs alloys is investigated both experimentally and theoretically based on a spin Hamiltonian analysis. We provide direct experimental evidence that the HFI between the electron and nuclear spin of the central Ga atom of the spin-filtering defect, namely, the Ga-i interstitials, causes strong mixing of the electron spin states of the defect, thereby degrading the efficiency of the spin-filtering effect. We also show that the HFI-induced spin mixing can be suppressed by an application of a longitudinal magnetic field such that the electronic Zeeman interaction overcomes the HFI, leading to well-defined electron spin states beneficial to the spin-filtering effect. The results provide a guideline for further optimization of the defect-engineered spin-filtering effect. DOI: 10.1103/PhysRevB.87.125202

    Place, publisher, year, edition, pages
    American Physical Society, 2013
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-90752 (URN)10.1103/PhysRevB.87.125202 (DOI)000316103800004 ()
    Note

    Funding Agencies|Linkoping University through the professor contract, Swedish Research Council|621-2011-4254|Linkoping University through the professor contract Swedish Energy Agency||Knut and Alice Wallenberg Foundation||

    Available from: 2013-04-08 Created: 2013-04-05 Last updated: 2017-12-06Bibliographically approved
    5. Limiting factor of defect-engineered spin-filtering effect at room temperature
    Open this publication in new window or tab >>Limiting factor of defect-engineered spin-filtering effect at room temperature
    2014 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 19, p. 195412-Article in journal (Refereed) Published
    Abstract [en]

    We identify hyperfine-induced electron and nuclear spin cross-relaxation as the dominant physical mechanism for the longitudinal electron spin relaxation time (T-1) of the spin-filtering Ga-i(2+) defects in GaNAs alloys. This conclusion is based on our experimental findings that T-1 is insensitive to temperature over 4-300 K, and its exact value is directly correlated with the hyperfine coupling strength of the defects that varies between different configurations of the Ga-i(2+) defects present in the alloys. These results thus provide a guideline for further improvements of the spin-filtering efficiency by optimizing growth and processing conditions to preferably incorporate the Ga-i(2+) defects with a weak hyperfine interaction and by searching for new spin-filtering defects with zero nuclear spin.

    Place, publisher, year, edition, pages
    American Physical Society, 2014
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-107449 (URN)10.1103/PhysRevB.89.195412 (DOI)000335913900007 ()
    Available from: 2014-06-12 Created: 2014-06-12 Last updated: 2017-12-05Bibliographically approved
    6. Room-Temperature Electron Spin Amplifier Base on Ga(In)NAs Alloys
    Open this publication in new window or tab >>Room-Temperature Electron Spin Amplifier Base on Ga(In)NAs Alloys
    Show others...
    2013 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 25, no 5, p. 738-742Article in journal (Refereed) Published
    Abstract [en]

    The first experimental demonstration of a spin amplifier at room temperature is presented. An efficient, defect-enabled spin amplifier based on a non-magnetic semiconductor, Ga(In)NAs, is proposed and demonstrated, with a large spin gain (up to 2700% at zero field) for conduction electrons and a high cut-off frequency up to 1 GHz.

    Keywords
    spin amplifiers; spintronics; room temperature; defects; semiconductors
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-85468 (URN)10.1002/adma.201202597 (DOI)000314600900008 ()
    Available from: 2012-11-20 Created: 2012-11-20 Last updated: 2017-12-07
    7. Efficient room-temperature spin detector based on GaNAs
    Open this publication in new window or tab >>Efficient room-temperature spin detector based on GaNAs
    Show others...
    2012 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 7, p. 07C303-Article in journal (Refereed) Published
    Abstract [en]

    Efficient and highly spin-dependent recombination processes are shown to not only turn GaNAs into an efficient spin filter but also to make it an excellent spin detector functional at room temperature (RT). By taking advantage of the defect-engineered spin-filtering effect, the spin detection efficiency is no longer limited by the fast spin relaxation of conduction electrons. This leads to a significant enhancement in the optical polarization of the spin detector, making it possible to reliably detect even very weak electron spin polarization at RT, as demonstrated by a study of spin loss during optical spin injection across a GaAs/GaNAs interface.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2012
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-78283 (URN)10.1063/1.3671781 (DOI)000303282401019 ()
    Available from: 2012-06-08 Created: 2012-06-08 Last updated: 2017-12-07
    8. Room-temperature spin injection and spin loss across a GaNAs/GaAs interface
    Open this publication in new window or tab >>Room-temperature spin injection and spin loss across a GaNAs/GaAs interface
    Show others...
    2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 1, p. 012112-Article in journal (Refereed) Published
    Abstract [en]

    Recently discovered effect of spin-filtering and spin amplification in GaNAs enables us to reliably obtain detailed information on the degree of spin loss during optical spin injection across a semiconductor heterointerface at room temperature. Spin polarization of electrons injected from GaAs into GaNAs is found to be less than half of what is generated in GaNAs by optical orientation. We show that the observed reduced spin injection efficiency is not only due to spin relaxation in GaAs, but more importantly due to spin loss across the interface due to structural inversion asymmetry and probably also interfacial point defects.

    Place, publisher, year, edition, pages
    American Institute of Physics, 2011
    National Category
    Engineering and Technology Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-65721 (URN)10.1063/1.3535615 (DOI)000286009800041 ()
    Note

    Original Publication: Yuttapoom Puttisong, Xiangjun Wang, Irina Buyanova, C W Tu, L Geelhaar, H Riechert and Weimin Chen, Room-temperature spin injection and spin loss across a GaNAs/GaAs interface, 2011, APPLIED PHYSICS LETTERS, (98), 1, 012112. http://dx.doi.org/10.1063/1.3535615 Copyright: American Institute of Physics http://www.aip.org/

    Available from: 2011-02-18 Created: 2011-02-18 Last updated: 2017-12-11
    9. Efficient room-temperature nuclear spin hyperpolarization of a defect atom in a semiconductor
    Open this publication in new window or tab >>Efficient room-temperature nuclear spin hyperpolarization of a defect atom in a semiconductor
    Show others...
    2013 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 4, no 1751Article in journal (Refereed) Published
    Abstract [en]

    Nuclear spin hyperpolarization is essential to future solid-state quantum computation using nuclear spin qubits and in highly sensitive magnetic resonance imaging. Though efficient dynamic nuclear polarization in semiconductors has been demonstrated at low temperatures for decades, its realization at room temperature is largely lacking. Here we demonstrate that a combined effect of efficient spin-dependent recombination and hyperfine coupling can facilitate strong dynamic nuclear polarization of a defect atom in a semiconductor at room temperature. We provide direct evidence that a sizeable nuclear field (~150 Gauss) and nuclear spin polarization (~15%) sensed by conduction electrons in GaNAs originates from dynamic nuclear polarization of a Ga interstitial defect. We further show that the dynamic nuclear polarization process is remarkably fast and is completed in <5 μs at room temperature. The proposed new concept could pave a way to overcome a major obstacle in achieving strong dynamic nuclear polarization at room temperature, desirable for practical device applications.

    Place, publisher, year, edition, pages
    Nature Publishing Group, 2013
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-93850 (URN)10.1038/ncomms2776 (DOI)000318872100108 ()
    Available from: 2013-06-11 Created: 2013-06-11 Last updated: 2017-12-06Bibliographically approved
  • 18.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Spin-dependent recombination in Ga(In)NAs alloys2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The abilities to control and manipulate electron spin, especially in semiconductors, lead to many interesting proposals for spin-functional devices in future spintronics and quantum information technology. A key requirement for the success of these proposals is that the spin functionality should be operational at room temperature (RT), which remains as a great challenge. Very recently, spin-dependent recombination (SDR) via paramagnetic defects that dominate in carrier recombination, i.e Gai - interstitial defects in Ga(In)NAs alloys, has been shown to turn the material into a highly efficient defectengineered spin filter operating at RT and without requiring an external applied field. This finding has demonstrated the great potential of such a spin filter as an efficient spin source, which is capable of generating up to 90% electron spin polarization at RT.

    Essential to realization of this attractive application in spintronics is a fundamental understanding of this alloy system and their related spin filtering defects. Therefore, factors controlling this spin filter must be studied, understood and optimized. In this licentiate thesis, we aim at optimization of the spin filtering effect in Ga(In)NAs alloys and the related quantum structures by studying influence of material fabrication techniques, post growth treatments and material structures. In paper I, we employed the optically detected magnetic resonance (ODMR) technique to study formation of Ga interstitial-related defects in Ga(In)NAs alloys. We showed that these spin-filtering defects are common grown-in defects in these alloys, independent of the employed fabrication techniques and post-growth annealing treatment. The defect formation was suggested to be thermodynamically favorable in the presence of nitrogen, possibly because of local strain compensation. In paper II, we further investigated the role of post-growth hydrogen treatment in the spin filtering effect in GaNAs epilayers and GaNAs/GaAs multiple quantum wells (QWs). From optical orientation studies, we found that the hydrogen treatment has led to nearly complete quenching of the spin filtering effect. Together with a detailed ODMR study and a rate equation analysis, the observed effect of hydrogen was attributed to hydrogen passivation of the spin filtering defects, likely by formation of complexes between the Gai-interstitial defects and hydrogen. This finding also ruled out the possibility of hydrogen as a part of the spin filtering defects in the as-grown materials, though hydrogen is known to be commonly present during the growth process.

    In Paper III, we examined the effectiveness of the spin filtering effect in the GaNAs/GaAs QWs as a function of QW width. Even with rather narrow QW widths of 3-9 nm, the spin filtering effect was shown to be efficient. It was further revealed that the spin filtering effect is more efficient in the wider QWs. From studies of transient behavior of photoluminescence and ODMR, it was concluded that this was mainly due to an increase in the sheet concentration of the spin filtering defects.

    List of papers
    1. Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials
    Open this publication in new window or tab >>Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials
    Show others...
    2009 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, p. 241904-Article in journal (Refereed) Published
    Abstract [en]

    Opticallydetected magnetic resonance measurements are carried out to study formationof Ga interstitial-related defects in Ga(In)NAs alloys. The defects, whichare among dominant nonradiative recombination centers that control carrier lifetimein Ga(In)NAs, are unambiguously proven to be common grown-in defectsin these alloys independent of the employed growth methods. Thedefects formation is suggested to become thermodynamically favorable because ofthe presence of nitrogen, possibly due to local strain compensation.

    Place, publisher, year, edition, pages
    American Institute of Physics, 2009
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-52858 (URN)10.1063/1.3275703 (DOI)
    Note
    Original Publication: Xingjun Wang, Yuttapoom Puttisong, C. W. Tu, Aaron J. Ptak, V. K. Kalevich, A. Yu. Egorov, L. Geelhaar, H. Riechert, Weimin Chen and Irina Buyanova, Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials, 2009, Applied Physics Letters, (95), 241904. http://dx.doi.org/10.1063/1.3275703 Copyright: American Institute of Physics http://www.aip.org/Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2017-12-12Bibliographically approved
    2. Room temperature spin filtering effect in GaNAs: Role of hydrogen
    Open this publication in new window or tab >>Room temperature spin filtering effect in GaNAs: Role of hydrogen
    Show others...
    2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 15, p. 152109-Article in journal (Refereed) Published
    Abstract [en]

    Effects of hydrogen on the recently discovered defect-engineered spin filtering in GaNAs are investigated by optical spin orientation and optically detected magnetic resonance. Post-growth hydrogen treatments are shown to lead to nearly complete quenching of the room-temperature spin-filtering effect in both GaNAs epilayers and GaNAs/GaAs multiple quantum wells, accompanied by a reduction in concentrations of Ga(i) interstitial defects. Our finding provides strong evidence for efficient hydrogen passivation of these spin-filtering defects, likely via formation of complexes between Gai defects and hydrogen, as being responsible for the Observed strong suppression of the spin-filtering effect after the hydrogen treatments.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2011
    Keywords
    gallium arsenide, gallium compounds, hydrogen, III-V semiconductors, interstitials, magnetic resonance, passivation, quenching (thermal), semiconductor epitaxial layers, semiconductor quantum wells, wide band gap semiconductors
    National Category
    Engineering and Technology Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-72139 (URN)10.1063/1.3651761 (DOI)000295883800045 ()
    Available from: 2011-11-18 Created: 2011-11-18 Last updated: 2017-12-08Bibliographically approved
    3. Electron spin filtering by thin GaNAs/GaAs multiquantum wells
    Open this publication in new window or tab >>Electron spin filtering by thin GaNAs/GaAs multiquantum wells
    Show others...
    2010 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 5, p. 052104-Article in journal (Refereed) Published
    Abstract [en]

    Effectiveness of the recently discovered defect-engineered spin-filtering effect is closely examined in GaNAs/GaAs multiquantum wells (QWs) as a function of QW width. In spite of narrow well widths of 3-9 nm, rather efficient spin filtering is achieved at room temperature. It leads to electron spin polarization larger than 18% and an increase in photoluminescence intensity by 65% in the 9 nm wide QWs. A weaker spin filtering effect is observed in the narrower QWs, mainly due to a reduced sheet concentration of spin-filtering defects (e.g., Ga-i interstitial defects).

    Keywords
    electron spin polarisation, gallium arsenide, III-V semiconductors, nitrogen compounds, photoluminescence, semiconductor quantum wells
    National Category
    Engineering and Technology Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-54084 (URN)10.1063/1.3299015 (DOI)000274319500045 ()
    Available from: 2010-02-22 Created: 2010-02-22 Last updated: 2017-12-12Bibliographically approved
  • 19.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Cavendish Laboratory, University of Cambridge.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Room Temperature Defect-Engineered Spin Functionalities: Concept and Optimization2017In: Contemporary Topics in Semiconductor Spintronics / [ed] Supriyo Bandyopadhyay (Virginia Commonwealth University, USA), Marc Cahay (University of Cincinnati, USA), Jean-Pierre Leburton (University of Illinois at Urbana-Champaign, USA), World Scientific, 2017Chapter in book (Other academic)
  • 20.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Limiting factor of defect-engineered spin-filtering effect at room temperature2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 19, p. 195412-Article in journal (Refereed)
    Abstract [en]

    We identify hyperfine-induced electron and nuclear spin cross-relaxation as the dominant physical mechanism for the longitudinal electron spin relaxation time (T-1) of the spin-filtering Ga-i(2+) defects in GaNAs alloys. This conclusion is based on our experimental findings that T-1 is insensitive to temperature over 4-300 K, and its exact value is directly correlated with the hyperfine coupling strength of the defects that varies between different configurations of the Ga-i(2+) defects present in the alloys. These results thus provide a guideline for further improvements of the spin-filtering efficiency by optimizing growth and processing conditions to preferably incorporate the Ga-i(2+) defects with a weak hyperfine interaction and by searching for new spin-filtering defects with zero nuclear spin.

  • 21.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Geelhaar, L
    Paul Drude Institute Festkorperelekt.
    Riechert, H
    Paul Drude Institute Festkorperelekt.
    Tu, C W
    University of California San Diego.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Efficient room-temperature spin detector based on GaNAs2012In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 7, p. 07C303-Article in journal (Refereed)
    Abstract [en]

    Efficient and highly spin-dependent recombination processes are shown to not only turn GaNAs into an efficient spin filter but also to make it an excellent spin detector functional at room temperature (RT). By taking advantage of the defect-engineered spin-filtering effect, the spin detection efficiency is no longer limited by the fast spin relaxation of conduction electrons. This leads to a significant enhancement in the optical polarization of the spin detector, making it possible to reliably detect even very weak electron spin polarization at RT, as demonstrated by a study of spin loss during optical spin injection across a GaAs/GaNAs interface.

  • 22.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Ptak, Aaron J.
    National Renewable Energy Laboratory, Golden, Colorado, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Geelhaar, Lutz
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Room-temperature defect-enabled electron spin amplifier in a non-magnetic semiconductor2013Conference paper (Other academic)
  • 23.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Ptak, Aaron J.
    National Renewable Energy Laboratory, Golden, Colorado.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Geelhaar, Lutz
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, Henning
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Room-Temperature Electron Spin Amplifier Base on Ga(In)NAs Alloys2013In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 25, no 5, p. 738-742Article in journal (Refereed)
    Abstract [en]

    The first experimental demonstration of a spin amplifier at room temperature is presented. An efficient, defect-enabled spin amplifier based on a non-magnetic semiconductor, Ga(In)NAs, is proposed and demonstrated, with a large spin gain (up to 2700% at zero field) for conduction electrons and a high cut-off frequency up to 1 GHz.

  • 24.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Ptak, Aaron. J.
    National Renewable Energy Laboratory, Golden, Colorado, USA.
    Tu, Charles W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Geelhaar, L.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    First demonstration of room-temperature electron spin amplifier based on Ga(In)NAs alloys2012Conference paper (Other academic)
  • 25.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Dagnelund, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C W
    Department of Electrical and Computer Engineering, University of California, La Jolla, California 92093, USA.
    Polimeni, A
    INFM and Dipartimento di Fisica, Universita` di Roma “La Sapienza,” Piazzale A. Moro 2, I-00185 Roma, Italy.
    Capizzi, M
    INFM and Dipartimento di Fisica, Universita` di Roma “La Sapienza,” Piazzale A. Moro 2, I-00185 Roma, Italy.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Room temperature spin filtering effect in GaNAs: Role of hydrogen2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 15, p. 152109-Article in journal (Refereed)
    Abstract [en]

    Effects of hydrogen on the recently discovered defect-engineered spin filtering in GaNAs are investigated by optical spin orientation and optically detected magnetic resonance. Post-growth hydrogen treatments are shown to lead to nearly complete quenching of the room-temperature spin-filtering effect in both GaNAs epilayers and GaNAs/GaAs multiple quantum wells, accompanied by a reduction in concentrations of Ga(i) interstitial defects. Our finding provides strong evidence for efficient hydrogen passivation of these spin-filtering defects, likely via formation of complexes between Gai defects and hydrogen, as being responsible for the Observed strong suppression of the spin-filtering effect after the hydrogen treatments.

  • 26.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dagnelund, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, Charles W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Polimeni, A.
    INFM and Dipartimento di Fisica, Università di Roma “La Sapienza”, Italy.
    Capizzi, M.
    INFM and Dipartimento di Fisica, Università di Roma, Italy .
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Effect of post-growth hydrogen treatment and annealing on spin filtering functionality in Ga(In)NAs alloys2012Conference paper (Other academic)
  • 27.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dagnelund, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, Charles W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Polimeni, A.
    INFM and Dipartimento di Fisica, Università di Roma, Italy.
    Capizzi, M.
    INFM and Dipartimento di Fisica, Università di Roma , Roma, Italy .
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Optimization of room-temperature defect-engineered spin filtering effect in Ga(In)NAs: rate equation studies2012Conference paper (Other academic)
  • 28.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Cavendish Laboratory, University of Cambridge.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Xia, Yuxin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin M.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Microscopic signature of the interfacial charge transfer states and their relevant spin-dependent processes in organic photovoltaics2016Conference paper (Refereed)
  • 29.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Huang, Yuqing
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Yang, X. J.
    Hokkaido University, Japan.
    Subagyo, A.
    Hokkaido University, Japan.
    Sueoka, K.
    Hokkaido University, Japan.
    Murayama, A.
    Hokkaido University, Japan.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Anomalous spectral dependence of optical polarization and its impact on spin detection in InGaAs/GaAs quantum dots2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 13, p. 132106-Article in journal (Refereed)
    Abstract [en]

    We show that circularly polarized emission light from InGaAs/GaAs quantum dot (QD) ensembles under optical spin injection from an adjacent GaAs layer can switch its helicity depending on emission wavelengths and optical excitation density. We attribute this anomalous behavior to simultaneous contributions from both positive and negative trions and a lower number of photo-excited holes than electrons being injected into the QDs due to trapping of holes at ionized acceptors and a lower hole mobility. Our results call for caution in reading out electron spin polarization by optical polarization of the QD ensembles and also provide a guideline in improving efficiency of spin light emitting devices that utilize QDs.

  • 30.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, X J.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Effect of hyperfine-induced spin mixing on the defect-enabled spin blockade and spin filtering in GaNAs2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 12Article in journal (Refereed)
    Abstract [en]

    The effect of hyperfine interaction (HFI) on the recently discovered room-temperature defect-enabled spin-filtering effect in GaNAs alloys is investigated both experimentally and theoretically based on a spin Hamiltonian analysis. We provide direct experimental evidence that the HFI between the electron and nuclear spin of the central Ga atom of the spin-filtering defect, namely, the Ga-i interstitials, causes strong mixing of the electron spin states of the defect, thereby degrading the efficiency of the spin-filtering effect. We also show that the HFI-induced spin mixing can be suppressed by an application of a longitudinal magnetic field such that the electronic Zeeman interaction overcomes the HFI, leading to well-defined electron spin states beneficial to the spin-filtering effect. The results provide a guideline for further optimization of the defect-engineered spin-filtering effect. DOI: 10.1103/PhysRevB.87.125202

  • 31.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, X. J.
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China .
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Role of hyperfine interaction on room room-temperature defect-enabled spin blockade and spin filtering functionalities in GaNAs alloys2013Conference paper (Other academic)
  • 32.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, X. J.
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China .
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Geelhaar, L.
    Paul-Drude-Institut fur Festkörpelektronik, Berlin, Germany.
    Ptak, A. J.
    National Renewable Energy Laboratory, Golden, Colorado, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Efficient room-temperature nuclear spin hyperpolarization of a defect atom in a semiconductor2013In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 4, no 1751Article in journal (Refereed)
    Abstract [en]

    Nuclear spin hyperpolarization is essential to future solid-state quantum computation using nuclear spin qubits and in highly sensitive magnetic resonance imaging. Though efficient dynamic nuclear polarization in semiconductors has been demonstrated at low temperatures for decades, its realization at room temperature is largely lacking. Here we demonstrate that a combined effect of efficient spin-dependent recombination and hyperfine coupling can facilitate strong dynamic nuclear polarization of a defect atom in a semiconductor at room temperature. We provide direct evidence that a sizeable nuclear field (~150 Gauss) and nuclear spin polarization (~15%) sensed by conduction electrons in GaNAs originates from dynamic nuclear polarization of a Ga interstitial defect. We further show that the dynamic nuclear polarization process is remarkably fast and is completed in <5 μs at room temperature. The proposed new concept could pave a way to overcome a major obstacle in achieving strong dynamic nuclear polarization at room temperature, desirable for practical device applications.

  • 33.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, X. J.
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China .
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Ptak, Aaron J.
    National Renewable Energy Laboratory, Golden, Colorado, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Geelhaar, Lutz
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Room-temperature spin functionality in non-magnetic semiconductor thin films and quantum structures2013Conference paper (Other academic)
  • 34.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C.W.
    University of California, La Jolla, USA .
    Geelhaar, L.
    Paul-Drude-Institut für Festkörpelektronik, Berlin.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, Berlin.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Studies of spin loss during room-temperature spin injection across a GaNAs/GaAs interface2011In: Abstract book of the 9th Int. Conf. on Nitride Semiconductors, Glasgow, UK, 2011, p. PC1.12-Conference paper (Other academic)
  • 35.
    Puttisong, Yuttapoom
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Carrere, H
    Université de Toulouse, LPCNO: INSA, UPS, CNRS, 135 avenue de Rangueil, 31077 Toulouse Cedex, France.
    Zhao, F
    Université de Toulouse, LPCNO: INSA, UPS, CNRS, 135 avenue de Rangueil, 31077 Toulouse Cedex, France.
    Balocchi, A
    Université de Toulouse, LPCNO: INSA, UPS, CNRS, 135 avenue de Rangueil, 31077 Toulouse Cedex, France.
    Marie, X
    Université de Toulouse, LPCNO: INSA, UPS, CNRS, 135 avenue de Rangueil, 31077 Toulouse Cedex, France.
    Tu, C W
    Department of Electrical and Computer Engineering, University of California, La Jolla, California 92093, USA.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Electron spin filtering by thin GaNAs/GaAs multiquantum wells2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 5, p. 052104-Article in journal (Refereed)
    Abstract [en]

    Effectiveness of the recently discovered defect-engineered spin-filtering effect is closely examined in GaNAs/GaAs multiquantum wells (QWs) as a function of QW width. In spite of narrow well widths of 3-9 nm, rather efficient spin filtering is achieved at room temperature. It leads to electron spin polarization larger than 18% and an increase in photoluminescence intensity by 65% in the 9 nm wide QWs. A weaker spin filtering effect is observed in the narrower QWs, mainly due to a reduced sheet concentration of spin-filtering defects (e.g., Ga-i interstitial defects).

  • 36.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Ptak, Aaron J.
    National Renewable Energy Laboratory, Golden, Colorado, USA.
    Tu, Charles W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Geelhaar, Lutz
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, Henning
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Defect-enabled Room-temperature Spin Functionality in Ga(In)NAs2012Conference paper (Other academic)
    Abstract [en]

    Efficient generation, maintaining, manipulation and detection of electron spin polarization and coherence at room-temperature (RT) in semiconductors is a prerequisite for the success of future semiconductor spintronics. Potential spintronic devices are expected to be based on fundamental building blocks such as spin filters (or spin injectors or spin aligners), spin amplifiers and spin detectors. During the past decade spin filters and spin detectors have been a main focal point of intense research efforts in the field of semiconductor spintronics that have led to many innovative approaches and encouraging developments. In contrast, experimental developments in spin amplifiers have been extremely limited. At present, realization of efficient RT spin functionality remains to be a great challenge and a hotly pursued research topic.

    In this work, we explore a new and unconventional approach of defect-enabled spin functionality in a non-magnetic semiconductor without requiring a magnetic layer or external magnetic fields. We demonstrated efficient defect-engineered spin filtering in Ga(In)NAs, which is capable of generating a remarkably high spin polarization degree (> 40%) of conduction electrons at RT. The highest spin polarization achieved to date by using this approach is up to 90 %. We also proposed a conceptually new spin amplifier by defect engineering and provided the first experimental demonstration of an efficient RT spin amplifier based on Ga(In)NAs with a spin gain up to 2700%! Such a spin amplifier is shown to be capable of amplifying a fast-modulating input spin signal while truthfully maintaining its time variation of the spin-encoded information, and is predicted to remain functional up to 1 GHz. By taking advantage of the spin amplification effect, we further showed that Ga(In)NAs can be employed as an efficient RT spin detector, with spin detection efficiency well exceeding 100%. Applications of such a spin-functional semiconductor material could potentially provide an attractive and viable solution to the current and important issues on RT spin injection, spin amplification and spin detection in semiconductors for future spintronics.

  • 37.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C W
    University California San Diego.
    Geelhaar, L
    Paul Drude Institut für Festkörperelektronik.
    Riechert, H
    Paul Drude Institut für Festkörperelektronik.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Room-temperature spin injection and spin loss across a GaNAs/GaAs interface2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 1, p. 012112-Article in journal (Refereed)
    Abstract [en]

    Recently discovered effect of spin-filtering and spin amplification in GaNAs enables us to reliably obtain detailed information on the degree of spin loss during optical spin injection across a semiconductor heterointerface at room temperature. Spin polarization of electrons injected from GaAs into GaNAs is found to be less than half of what is generated in GaNAs by optical orientation. We show that the observed reduced spin injection efficiency is not only due to spin relaxation in GaAs, but more importantly due to spin loss across the interface due to structural inversion asymmetry and probably also interfacial point defects.

  • 38.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Xia, Yuxin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, X.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Charge Generation via Relaxed Charge-Transfer States in Organic Photovoltaics by an Energy-Disorder-Driven Entropy Gain2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 24, p. 12640-12646Article in journal (Refereed)
    Abstract [en]

    In organic photovoltaics, efficient charge generation relies on our ability to convert excitons into free charges. Efficient charge separation from "energetic excitons" has been understood to be governed by delocalization effects promoted by molecular aggregation. A remaining puzzle is, however, the mechanism underlying charge generation via relaxed interfacial charge-transfer (CT) excitons that also exhibit an internal quantum efficiency close to unity. Here, we provide evidence for efficient charge generation via CT state absorption over a temperature range of 50-300 K, despite an intrinsically strong Coulomb binding energy of about 400 meV that cannot be modified by fullerene aggregation. We explain our observation by entropy-driven charge separation, with a key contribution from energy disorder. The energy disorder reduces the charge generation barrier by substantially gaining the entropy as electron hole distance increases, resulting in efficient CT exciton dissociation. Our results underline an emerging consideration of energy disorder in thermodynamic stability of charge pairs and highlight the energy disorder as a dominant factor for generating charges via the CT state. A discussion for a trade-off in harvesting charges from relaxed CT excitons is also provided.

  • 39.
    Wang, Suhao
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Sun, Hengda
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Erdmann, Tim
    Tech Univ Dresden, Germany; Leibniz Inst Polymerforsch Dresden eV, Germany; Flexterra Corp, IL 60077 USA; IBM Almaden Res Ctr, CA 95120 USA.
    Wang, Gang
    Northwestern Univ, IL 60208 USA.
    Fazzi, Daniele
    Max Planck Inst Kohlenforsch, Germany; Univ Cologne, Germany.
    Lappan, Uwe
    Leibniz Inst Polymerforsch Dresden eV, Germany.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Chen, Zhihua
    Flexterra Corp, IL 60077 USA.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Kiriy, Anton
    Tech Univ Dresden, Germany; Leibniz Inst Polymerforsch Dresden eV, Germany.
    Voit, Brigitte
    Tech Univ Dresden, Germany; Leibniz Inst Polymerforsch Dresden eV, Germany.
    Marks, Tobin J.
    Northwestern Univ, IL 60208 USA; Northwestern Univ, IL 60208 USA.
    Fabiano, Simone
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering. Flexterra Corp, IL 60077 USA; Northwestern Univ, IL 60208 USA; Northwestern Univ, IL 60208 USA.
    Facchetti, Antonio
    Flexterra Corp, IL 60077 USA; Northwestern Univ, IL 60208 USA; Northwestern Univ, IL 60208 USA.
    A Chemically Doped Naphthalenediimide-Bithiazole Polymer for n-Type Organic Thermoelectrics2018In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 30, no 31, article id 1801898Article in journal (Refereed)
    Abstract [en]

    The synthesis of a novel naphthalenediimide (NDI)-bithiazole (Tz2)-based polymer [P(NDI2OD-Tz2)] is reported, and structural, thin-film morphological, as well as charge transport and thermoelectric properties are compared to the parent and widely investigated NDI-bithiophene (T2) polymer [P(NDI2OD-T2)]. Since the steric repulsions in Tz2 are far lower than in T2, P(NDI2OD-Tz2) exhibits a more planar and rigid backbone, enhancing p-p chain stacking and intermolecular interactions. In addition, the electron-deficient nature of Tz2 enhances the polymer electron affinity, thus reducing the polymer donor-acceptor character. When n-doped with amines, P(NDI2OD-Tz2) achieves electrical conductivity (approximate to 0.1 S cm(-1)) and a power factor (1.5 mu W m(-1) K-2) far greater than those of P(NDI2OD-T2) (0.003 S cm(-1) and 0.012 mu W m(-1) K-2, respectively). These results demonstrate that planarized NDI-based polymers with reduced donor-acceptor character can achieve substantial electrical conductivity and thermoelectric response.

  • 40.
    Wang, Xingjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Carrère, Hélène
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Zhao, F
    n/a.
    Balocchi, A
    n/a.
    Marie, X
    n/a.
    Tu, C W
    n/a.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Efficient room temperature spin filter based on GaNAs quantum wells2009In: Abstract Book of the 14th International Conference on Modulated Semiconductor structures (MSS-14), Kobe, Japan, July 19 - 24, 2009, 2009, p. 161-Conference paper (Other academic)
  • 41.
    Wang, Xingjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California 92093, USA.
    Ptak, Aaron J.
    National Renewable Energy Laboratory, Golden, Colorado 80401, USA.
    Kalevich, V. K.
    A. F. Ioffe Physico-Technical Institute, St. Petersburg 194021, Russia.
    Egorov, A. Yu.
    A. F. Ioffe Physico-Technical Institute, St. Petersburg 194021, Russia.
    Geelhaar, L.
    Paul-Drude-Institut für Festkörpelektronik, 10117 Berlin, Germany.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, 10117 Berlin, Germany.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, p. 241904-Article in journal (Refereed)
    Abstract [en]

    Opticallydetected magnetic resonance measurements are carried out to study formationof Ga interstitial-related defects in Ga(In)NAs alloys. The defects, whichare among dominant nonradiative recombination centers that control carrier lifetimein Ga(In)NAs, are unambiguously proven to be common grown-in defectsin these alloys independent of the employed growth methods. Thedefects formation is suggested to become thermodynamically favorable because ofthe presence of nitrogen, possibly due to local strain compensation.

  • 42.
    Wang, Xingjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, Charles W
    Ptak, Aaron J
    Kalevich, Vladimir K
    Egorov, A Y
    Geelhaar, L
    Riechert, H
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Spin-blockade of dominant non-radiative carrier recombination channels via defects in Ga(In)NAs alloys2010In: Abstract Book of the MRS Spring Meeting, San Francisco, USA, April 5-9, 2010, 2010, p. EE6.6-Conference paper (Other academic)
  • 43.
    Wang, Xingjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, Charles W
    Ptak, Aaron J
    Kalevich, Vladimir K
    Egorov, A Y
    Geelhaar, L
    Riechert, H
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Spin-engineered suppression of dominant non-radiative shunt paths in Ga(In)NAs relevant to photovoltaic applications2010In: Abstract Book of the Materials Challenges in Alternative & Renewable Energy conference, 2010, p. 36-Conference paper (Other academic)
  • 44.
    Wang, Xingjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C.W.
    University of California.
    Ptak, Aaron J.
    National Renewable Energy Laboratory, Golden, Colorado.
    Kalevich, V.K.
    A.F. Ioffe Physico-Technical Institute, St-Petersburg.
    Egorov, A.Yu
    A. F. Ioffe Physico-Technical Institute, St. Petersburg.
    Geelhaar, L.
    Paul-Drude-Institut für Festkörpelektronik, Berlin.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, Berlin.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Engineering spin-dependent carrier recombination processes in Ga(In)NAs for optoelectronic and photovoltaic applications2011In: Abstract Book of  the Int. Conf. on Fundamental Optical Processes in Semiconductors, Lake Junaluska, USA, 2011, p. PB3.-Conference paper (Other academic)
  • 45.
    Zhao, Baodan
    et al.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Abdi-Jalebi, Mojtaba
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Tabachnyk, Maxim
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Glass, Hugh
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Kamboj, Varun S.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Nie, Wanyi
    Los Alamos National Laboratory, Los Alamos, NM, USA.
    Pearson, Andrew J.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering. Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Gödel, Karl C.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Beere, Harvey E.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Ritchie, David A.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Mohite, Aditya D.
    Los Alamos National Laboratory, Los Alamos, NM, USA.
    Dutton, Siân E.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Friend, Richard H.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Sadhanala, Aditya
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    High Open-Circuit Voltages in Tin-Rich Low-Bandgap Perovskite-Based Planar Heterojunction Photovoltaics2017In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 29, article id 1604744Article in journal (Refereed)
    Abstract [en]

    Low-bandgap CH3NH3(PbxSn1–x)I3 (0 ≤ x ≤ 1) hybrid perovskites (e.g., ≈1.5–1.1 eV) demonstrating high surface coverage and superior optoelectronic properties are fabricated. State-of-the-art photovoltaic (PV) performance is reported with power conversion efficiencies approaching 10% in planar heterojunction architecture with small (<450 meV) energy loss compared to the bandgap and high (>100 cm2 V−1s−1) intrinsic carrier mobilities.

1 - 45 of 45
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