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  • 1.
    Adnane, Bouchaib
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hansson, Göran
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ni, Wei-Xin
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Photoluminescence excitation spectroscopy of self-assembled SiGe/Si quantum dots2009Manuscript (preprint) (Other academic)
    Abstract [en]

    Photoluminescence excitation (PLE) experiments are reported for various self-assembled SiGe/Si dot samples grown on Si(001) by molecular beam epitaxy at substrate temperatures ranging from 430 to 580 C. Two excitation peaks were observed, and the characteristics of the involved optical transitions were studied in detail by PLE (in one case implemented together with selective photoluminescence, SPL) on different samples containing either only one SiGe dot layer or multiple SiGe-dot/Si stacks. The temperature- and power-dependence of the excitation properties together with the results of six-band k.p calculations support the assignment of the observed PLE peaks to spatially direct and indirect transitions collected from two different SiGe dot populations.

  • 2.
    Adnane, Bouchaib
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hansson, Göran
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ni, Wei-Xin
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Spatially direct and indirect transitions of self-assembled SiGe/Si quantum dots studied by photoluminescence excitation spectroscopy2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 18, p. 181107-Article in journal (Refereed)
    Abstract [en]

    Well-resolved photoluminescence excitation (PLE) spectra are reported for selfassembled SiGe dots grown on Si(100) by molecular beam epitaxy. The observation of two excitation resonance peaks is attributed to two different excitation/de-excitation routes of interband optical transitions connected to the spatially direct and indirect recombination processes. It is concluded that two dot populations are addressed by each monitored luminescence energy for the PLE acquisition.

  • 3.
    Adnane, Bouchaib
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Zhao, Ming
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Hansson, Göran
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ni, Wei-Xin
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Origin of photoresponse at 8-14 μm in stacks of self-assembled SiGe/Si quantum dots2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235XArticle in journal (Other academic)
    Abstract [en]

    A normal incidence photodetector operating at 8-14 μm is demonstrated using p-type δ-doped SiGe dot multilayer structures grown by molecular beam epitaxy on Si(001) substrates. Based on the experimental results of photoluminescence and photoluminescence excitation spectroscopies together with numerical analysis, the origin of the measured photocurrent was attributed to intersubband optical transitions between the heavy hole and light hole states of the valence band of the self-assembled SiGe dots and subsequent lateral transport of photo-excited carriers in the conduction channels formed by Ge wetting layers.

  • 4.
    Adnane, Bouchaib
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Lai, Yi-Fan
    National Nano Device Labs, Taiwan.
    Shieh, Jia-Min
    National Nano Device Labs, Taiwan.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ni, Wei-Xin
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Photoluminescence study of nanocrystalline-Si(Ge) embedded in mesoporous silica2009In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 53, no 8, p. 862-864Article in journal (Refereed)
    Abstract [en]

    Photoluminescence (PL) properties of mesoporous silica (MS) samples incorporated with Si or Ge nanocrystals (nc) have been investigated with various excitation powers and post-RTA processes. The analysis of experimental results revealed a superlinear intensity dependence (m = 1.7) in the MS reference sample without nanocrystals, while a sublinear behavior (m = 0.8) is observed for the nc-Si in MS. It thus suggests the same recombination responsible for the luminescence at similar to 2.75 eV for both samples, but different kinetic limitations for the carrier transfer processes. Si nanocrystals play in this case an important role in generating more photo-excited carriers, enhancing the PL intensity.

  • 5.
    Agekyan, V F
    et al.
    n/a.
    Holtz, P O
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Karczewski, G
    n/a.
    Moskalenko, E S
    n/a.
    Yu, A
    n/a.
    Serov, x
    n/a.
    Filosofov, N G
    n/a.
    Exciton localization and sp-d energy transfer in CdMnTe/CdMgTe nanostructures with ultrathin narrow-gap magnetic layers2009In: 17th Int. Symp. “Nanostructures: Physics and Technology”, 2009Conference paper (Refereed)
  • 6.
    Agekyan, V F
    et al.
    St Petersburg State University.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karczewski, G
    Polish Acadamy of Science.
    Moskalenko, E S
    Russian Acadamy of Science.
    Yu Serov, A
    St Petersburg State University.
    Filosofov, N G
    St Petersburg State University.
    Effect of a magnetic field on energy transfer of band states to the Mn2+ 3d shell in the CdMgTe matrix with ultrathin CdMnTe layers2010In: PHYSICS OF THE SOLID STATE, ISSN 1063-7834, Vol. 52, no 1, p. 27-31Article in journal (Refereed)
    Abstract [en]

    The effect of external magnetic fields on two radiative (band-to-band and on-site) recombination channels in II-VI dilute magnetic semiconductors and related nanostructures has been considered. The 3d on-site emission of manganese ions in CdMgTe matrices containing periodic inclusions of CdMnTe narrow-band-gap layers with thicknesses of 0.5, 1.5, and 3.0 monolayers has been investigated in magnetic fields of up to 6 T. It has been shown that, in a magnetic field, luminescence of manganese ions weakens because of the decrease in the rate of spin-dependent excitation transfer from band states to the Mn2+ 3d shell. The maximum suppression of 3d luminescence has been observed in the matrix with a CdMnTe layer 3.0 monolayers thick. This indicates that the main factor responsible for the energy transfer is the internal field near the CdMnTe layers, which determines the magnetic splitting and spin polarization of band states.

  • 7.
    Agekyan, V F
    et al.
    St Petersburg State University.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karczewski, G
    Polish Academy of Science.
    N Katz, V
    St Petersburg State University.
    Moskalenko, E S
    Russian Academy of Science.
    Yu Serov, A
    St Petersburg State University.
    Filosofov, N G
    St Petersburg State University.
    Magnetoluminescence of CdTe/MnTe/CdMgTe heterostructures with ultrathin MnTe layers2011In: Semiconductors (Woodbury, N.Y.), ISSN 1063-7826, E-ISSN 1090-6479, Vol. 45, no 10, p. 1301-1305Article in journal (Refereed)
    Abstract [en]

    CdTe/MnTe/CdMgTe quantum-well structures with one or two monolayers of MnTe inserted at CdTe/CdMgTe interfaces were fabricated. The spectra of the excitonic luminescence from CdTe quantum wells and their variation with temperature indicate that introduction of ultrathin MnTe layers improves the interface quality. The effect of a magnetic field in the Faraday configuration on the spectral position of the exciton-emission peaks indicates that frustration of magnetic moments in one-monolayer MnTe insertions is weaker than in two-monolayer insertions. The effect of a magnetic field on the exciton localization can be explained in terms of the exciton wave-function shrinkage and obstruction of the photoexcited charge-carrier motion in the quantum well.

  • 8.
    Aleksandrov, I.A.
    et al.
    Russian Academy of Science.
    Zhuravlev, K.S.
    Russian Academy of Science.
    Mansurov, V.G.
    Russian Academy of Science.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Linearly polarized photoluminescence from an ensemble of wurtzite GaN/AlN quantum dots2010In: JETP Letters: Journal of Experimental And Theoretical Physics Letters, ISSN 0021-3640, E-ISSN 1090-6487, Vol. 91, no 9, p. 452-454Article in journal (Refereed)
    Abstract [en]

    Microphotoluminescence from GaN/AlN quantum dots grown by molecular beam epitaxy on sapphire substrates along the (0001) axis has been studied. To produce quantum dots of different average sizes and densities, the nominal amount of deposited GaN has been varied from 1 to 4 ML. The density of the quantum dots was about 10(11) cm(-2), which corresponded to about 10(3) quantum dots excited in the experiments. The photo-luminescence from the quantum dots was linearly polarized and the maximum polarization degree (15%) has been observed for the sample with the lowest amount of deposited GaN. The photoluminescence intensity from this sample under continuous laser excitation decreased by more than two orders of magnitude for about 30 min and then stabilized. The photoluminescence intensity from other samples under continuous excitation remained constant. We suggest that a rather high polarization degree is caused by anisotropy in the strain and shape of the quantum dots formed near the dislocations, which also act as the centers of nonradiative recombination.

  • 9.
    Amloy, Supaluck
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Chen, Y T
    Acad Sinica, Taiwan .
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Chen, K H
    Acad Sinica, Taiwan .
    Hsu, H C
    National Taiwan University.
    Hsiao, C L
    National Taiwan University.
    Chen, L C
    National Taiwan University.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Polarization-resolved fine-structure splitting of zero-dimensional InxGa1-xN excitons2011In: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 83, no 20, p. 201307-Article in journal (Refereed)
    Abstract [en]

    The fine-structure splitting of quantum confined InxGa1-x Nexcitons is investigated using polarization-sensitive photoluminescence spectroscopy. The majority of the studied emission lines exhibits mutually orthogonal fine-structure components split by 100-340 mu eV, as measured from the cleaved edge of the sample. The exciton and the biexciton reveal identical magnitudes but reversed sign of the energy splitting.

  • 10.
    Amloy, Supaluck
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Andersson, T. G.
    Applied Semiconductor Physics, Department of Microtechnology and Nanoscience, Chalmers University.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    On the polarized emission from exciton complexes in GaN quantum dots2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 021901Article in journal (Refereed)
    Abstract [en]

    The optical linear polarization properties of exciton complexes in asymmetric Stranski-Krastanov grown GaN quantum dots have been investigated experimentally and theoretically. It is demonstrated that the polarization angle and the polarization degree can be conveniently employed to associate emission lines in the recorded photoluminescence spectra to a specific dot. The experimental results are in agreement with configuration interaction computations, which predict similar polarization degrees for the exciton and the biexciton (within 10%) in typical GaN quantum dots. The theory further predicts that the polarization degree can provide information about the charge state of the dot.

  • 11.
    Amloy, Supaluck
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    III-nitride based quantum dots for photon emission with controlled polarization switchingManuscript (preprint) (Other academic)
    Abstract [en]

    Computational studies based on 6 band k⋅p!theory are employed on lens-shaped III-nitride quantum dots (QDs) with focus on the polarization properties of the optical interband transitions. The results predict pronounced linear polarization of the ground-state related transitions for asymmetric QDs of a material with small split-off energy. It is demonstrated that a moderate externally applied electric field can be used to induce a linear polarization and to control its direction. InN is found to be the most efficient choice for dynamic polarization switching controlled by an electric field, with potential for polarization control on a photon-by-photon level.

  • 12.
    Amloy, Supaluck
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Chen, Y. T.
    Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan.
    Chen, K. H.
    Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan.
    Hsu, H. C.
    Center for Condensed Matter Sciences, National Taiwan University, Taiwan.
    Hsiao, C. L.
    Center for Condensed Matter Sciences, National Taiwan.
    Chen, L. C.
    Center for Condensed Matter Sciences, National Taiwan.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Excitons and biexcitons in InGaN quantum dot like localization centersManuscript (preprint) (Other academic)
    Abstract [en]

    Indium segregation in a narrow InGaN single quantum well creates quantum dot (QD) like exciton localization centers. Cross section transmission electron microscopy reveals varying shapes and lateral sizes in the range ~1-5 nm of the QD-like features, while scanning near field optical microscopy demonstrates a highly inhomogeneous spatial distribution of optically active individual localization centers. Microphotoluminescence spectroscopy confirms the spectrally inhomogeneous distribution of localization centers, in which the exciton and the biexciton related emissions from single centers of varying geometry could be identified by means of excitation power dependencies. Interestingly, the biexciton binding energy (Ebxx) was found to vary from center to center, between 3 to -22 meV, in correlation with the exciton emission energy. Negative binding energies justify the three-dimensional quantum confinement, which confirms QD-like properties of the localization centers.! The observed energy correlation is proposed to be understood as variations of the lateral extension of the confinement potential, which would yield smaller values of Ebxx for reduced lateral extension and higher exciton emission energy. The proposed relation between lateral extension and Ebxx is further supported by the exciton and the biexciton recombination lifetimes of a single QD, which suggest a lateral extension of merely ~3 nm for a QD with strongly negative Ebxx = -15.5 meV.

  • 13.
    Amloy, Supaluck
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology. Thaksin University, Thailand.
    Karlsson, K. Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Eriksson, Martin O
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Chen, Y. T.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology. Academia Sinica, Taiwan .
    Chen, K. H.
    Academia Sinica, Taiwan; National Taiwan University, Taiwan.
    Hsu, H. C.
    National Taiwan University, Taiwan.
    Hsiao, C. L.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. National Taiwan University, Taiwan.
    Chen, L. C.
    National Taiwan University, Taiwan.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Excitons and biexcitons in InGaN quantum dot like localization centers2014In: Nanotechnology, ISSN 0957-4484, Vol. 25, no 49, p. 495702-Article in journal (Refereed)
    Abstract [en]

    Indium segregation in a narrow InGaN single quantum well creates quantum dot (QD) like exciton localization centers. Cross-section transmission electron microscopy reveals varying shapes and lateral sizes in the range ∼1–5 nm of the QD-like features, while scanning near field optical microscopy demonstrates a highly inhomogeneous spatial distribution of optically active individual localization centers. Microphotoluminescence spectroscopy confirms the spectrally inhomogeneous distribution of localization centers, in which the exciton and the biexciton related emissions from single centers of varying geometry could be identified by means of excitation power dependencies. Interestingly, the biexciton binding energy (Ebxx) was found to vary from center to center, between 3 to −22 meV, in correlation with the exciton emission energy. Negative binding energies are only justified by a three-dimensional quantum confinement, which confirms QD-like properties of the localization centers. The observed energy correlation is proposed to be understood as variations of the lateral extension of the confinement potential, which would yield smaller values of Ebxx for reduced lateral extension and higher exciton emission energy. The proposed relation between lateral extension and Ebxx is further supported by the exciton and the biexciton recombination lifetimes of a single QD, which suggest a lateral extension of merely ∼3 nm for a QD with strongly negative Ebxx = −15.5 meV. 

  • 14.
    Amloy, Supaluck
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Moskalenko, Evgenii
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Eriksson, M
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, K Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Chen, Y T
    Academic Sinica, Taiwan .
    Chen, K H
    Academic Sinica, Taiwan National Taiwan University, Taiwan .
    Hsu, H C
    National Taiwan University, Taiwan .
    Hsiao, C L
    National Taiwan University, Taiwan .
    Chen, L C
    National Taiwan University, Taiwan .
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Dynamic characteristics of the exciton and the biexciton in a single InGaN quantum dot2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 6Article in journal (Refereed)
    Abstract [en]

    The dynamics of the exciton and the biexciton related emission from a single InGaN quantum dot (QD) have been measured by time-resolved microphotoluminescence spectroscopy. An exciton-biexciton pair of the same QD was identified by the combination of power dependence and polarization-resolved spectroscopy. Moreover, the spectral temperature evolution was utilized in order to distinguish the biexciton from a trion. Both the exciton and the biexciton related emission reveal mono-exponential decays corresponding to time constants of similar to 900 and similar to 500 ps, respectively. The obtained lifetime ratio of similar to 1.8 indicates that the QD is small, with a size comparable to the exciton Bohr radius.

  • 15.
    Amloy, Supaluck
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yu, K. H.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Farivar, R
    Applied Semiconductor Physics, Department of Microtechnology and Nanoscience, Chalmers University of Technology, S-41296 Göteborg, Sweden .
    Andersson, T. G.
    Applied Semiconductor Physics, Department of Microtechnology and Nanoscience, Chalmers University of Technology, S-41296 Göteborg, Sweden .
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Size dependent biexciton binding energies in GaN quantum dots2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 25, no 251903Article in journal (Refereed)
    Abstract [en]

    Single GaN/Al(Ga)N quantum dots (QDs) have been investigated by means of microphotoluminescence. Emission spectra related to excitons and biexcitons have been identified by excitation power dependence and polarization resolved spectroscopy. All investigated dots exhibit a strong degree of linear polarization (∼90%). The biexciton binding energy scales with the dot size. However, both positive and negative binding energies are found for the studied QDs. These results imply that careful size control of III-Nitride QDs would enable the emission of correlated photons with identical frequencies from the cascade recombination of the biexciton, with potential applications in the area of quantum information processing.

  • 16.
    Amloy, Supaluck
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology. Department of Physics, Faculty of Science, Thaksin University, 93110 Phattalung, Thailand .
    Yu, K. H.
    Linköping University, Department of Physics, Chemistry and Biology.
    Karlsson, K Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Farivar, R.
    Applied Semiconductor Physics, Department of Microtechnology and Nanoscience, Chalmers University of Technology, S‐41296 Göteborg, Sweden.
    Andersson, T. G.
    Applied Semiconductor Physics, Department of Microtechnology and Nanoscience, Chalmers University of Technology, S‐41296 Göteborg, Sweden.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Polarized Emission from Single GaN Quantum Dots Grown by Molecular Beam Epitaxy2011Conference paper (Other academic)
    Abstract [en]

    Polarization resolved microphotoluminescence measurements of single MBE‐grown GaN/Al(Ga)N quantum dots (QDs) have been performed. The exciton and biexciton peaks with full width at half maximum as narrow as <500 μeV  were observed. Interestingly, there exist both positive and negative binding energies of the biexciton, explained in term of different sizes of the measured dots, resulting in different built‐in electric field. Moreover, a strongly linearly polarized emission is observed for the investigated dots with a degree of linear polarization of about 0.9, interpreted as the valence‐band mixing induced by in‐plane anisotropy due to strain and/or QD shape.

  • 17.
    Amloy, Supaluck
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Department of Physics, Faculty of Science, Thaksin University, 93110 Phattalung, Thailand .
    Yu, K.H.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Farivar, R
    Applied Semiconductor Physics, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg, Sweden.
    Andersson, Torwald
    Applied Semiconductor Physics, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg, Sweden.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Polarized Emission from Single GaN Quantum Dot Grown by Molecular Beam Epitaxy2011Conference paper (Refereed)
    Abstract [en]

    Polarization resolved microphotoluminescence measurements of single MBE‐grown GaN∕Al(Ga)N quantum dots (QDs) have been performed. The exciton and biexciton peaks with full width at half maximum as narrow as <500 μeV were observed. Interestingly, there exist both positive and negative binding energies of the biexciton, explained in term of different sizes of the measured dots, resulting in different built‐in electric field. Moreover, a strongly linearly polarized emission is observed for the investigated dots with a degree of linear polarization of about 0.9, interpreted as the valence‐band mixing induced by in‐plane anisotropy due to strain and∕or QD shape.

  • 18.
    Andersson, J. Y.
    et al.
    Acreo AB.
    Hoglund, L.
    Acreo AB .
    Noharet, B.
    Acreo AB.
    Wang, Q.
    Acreo AB.
    Ericsson, P.
    Acreo AB.
    Wissmar, S.
    Acreo AB.
    Asplund, C.
    IRnova AB.
    Malm, H.
    IRnova AB.
    Martijn, H.
    IRnova AB.
    Hammar, M.
    Royal Institute of Technology, Stockholm.
    Gustafsson, O.
    Royal Institute of Technology, Stockholm.
    Hellstrom, S.
    Royal Institute of Technology, Stockholm.
    Radamson, H.
    Royal Institute of Technology, Stockholm.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Quantum structure based infrared detector research and development within Acreos centre of excellence IMAGIC2010In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 53, no 4, p. 227-230Article in journal (Refereed)
    Abstract [en]

    Acreo has a long tradition of working with quantum structure based infrared (IR) detectors and arrays. This includes QWIP (quantum well infrared photodetector), QDIP (quantum dot infrared photodetector), and InAs/GaInSb based photon detectors of different structure and composition. It also covers RandD on uncooled microbolometers. The integrated thermistor material of such detectors is advantageously based on quantum structures that are optimised for high temperature coefficient and low noise. Especially the SiGe material system is preferred due to the compatibility with silicon technology. The RandD work on IR detectors is a prominent part of Acreos centre of excellence "IMAGIC" on imaging detectors and systems for non-visible wavelengths. IMAGIC is a collaboration between Acreo, several industry partners and universities like the Royal Institute of Technology (KTH) and Linkoping University.

  • 19. Arnaudov, B.
    et al.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Harati Zadeh, Hamid
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kamiyama, S.
    Iwaya, M.
    Amano, H.
    Akasaki, I.
    Radiative recombination mechanism in highly modulation doped GaN/AlGaN multiple quantum wells2006In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 6, p. 1888-1891Article in journal (Refereed)
  • 20.
    Bergman, Peder
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Dalfors, J.
    Sernelius, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Amano, H.
    Akasaki, I.
    Radiative recombination in InGaN/GaN multiple quantum well2000In: ICSCRM 99,1999, 2000, p. 1571-Conference paper (Refereed)
  • 21.
    Chen, Ruei-San
    et al.
    National Taiwan University of Science and Technology, Taiwan.
    Tang, Chih-Che
    Department of Electronic Engineering, National Taiwan University of Science and Technology, Taiwan.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Holtz, Per Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Electronic transport properties in aluminum indium nitride nanorods grown by magnetron sputter epitaxy2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 285, p. 625-628Article in journal (Refereed)
    Abstract [en]

    The electronic transport properties of the wide-bandgap aluminum indium nitride (AlInN) nanorods (NRs) grown by ultrahigh-vacuum magnetron sputter epitaxy (MSE) have been studied. The conductivities of the ternary compound nanostructure locates at the value of 15 Q-1 cm -1, which is respectively one and two orders of magnitude lower than the binary GaN and InN counterparts grown by chemical vapor deposition (CVD). The very shallow donor level/band with the activation energy at 11 + 2 meV was obtained by the temperature-dependent measurement. In addition, the photoconductivity has also been investigated. The photoconductive (PC) gain of the NRs device can reach near 2400 under a low bias at 0.1 V and the light intensity at 100W m-2 for ultraviolet response in vacuum. The power-insensitive gain and ambience-dependent photocurrent are also observed, which is attributed to the probable surfacecontrolled PC mechanism in this ternary nitride nanostructure.

  • 22.
    Chen, Yen-Ting
    et al.
    Academic Sinica, Taiwan .
    Araki, Tsutomu
    Ritsumeikan University, Japan .
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Chen, Li-Chyong
    National Taiwan University, Taiwan .
    Chen, Kuei-Hsien
    Academic Sinica, Taiwan .
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nanishi, Yasushi
    Ritsumeikan University, Japan .
    Nucleation of single GaN nanorods with diameters smaller than 35 nm by molecular beam epitaxy2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 20, p. 203108-Article in journal (Refereed)
    Abstract [en]

    Nucleation mechanism of catalyst-free GaN nanorod grown on Si(111) is investigated by the fabrication of uniform and narrow (andlt; 35 nm) nanorods without a pre-defined mask by molecular beam epitaxy. Direct evidences show that the nucleation of GaN nanorods stems from the sidewall of the underlying islands down to the Si(111) substrate, different from commonly reported ones on top of the island directly. Accordingly, the growth and density control of the nanorods is exploited by a "narrow-pass" approach that only narrow nanorod can be grown. The optimal size of surrounding non-nucleation area around single nanorod is estimated as 88 nm.

  • 23.
    Chen, Yen-Ting
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Karlsson, K. Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Determination of critical diameters for intrinsic carrier diffusion-length of GaN nanorods with cryo-scanning near-field optical microscopy2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, no 21482, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Direct measurements of carrier diffusion in GaN nanorods with a designed InGaN/GaN layer-in-a-wire structure by scanning near-field optical microscopy (SNOM) were performed at liquid-helium temperatures of 10 K. Without an applied voltage, intrinsic diffusion lengths of photo-excited carriers were measured as the diameters of the nanorods differ from 50 to 800 nm. The critical diameter of nanorods for carrier diffusion is concluded as 170 nm with a statistical approach. Photoluminescence spectra were acquired for different positions of the SNOM tip on the nanorod, corresponding to the origins of the well-defined luminescence peaks, each being related to recombination-centers. The phenomenon originated from surface oxide by direct comparison of two nanorods with similar diameters in a single map has been observed and investigated.

  • 24. Donchev, V.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Moskalenko, Evgenii
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, J.M.
    Garcia, J.M.
    Petroff, M.
    Temperature Study of the Photoluminescence of a Single InAs/GaAs Quantum Dot2004In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 3, p. 608-Article in journal (Refereed)
    Abstract [en]

    Presented at: The 8th Conference on Optics of Excitons in Confined Systems, Lecce, Italy, February 3 - 4, 2003

  • 25. Donchev, V.
    et al.
    Moskalenko, Evgenii
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Karlsson, K.F.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Materials Department, University of California, Santa Barbara, CA 93106, United States.
    Garcia, J.M.
    Institute de Microelectronica de Madrid, CNM-CSIC Isaak Newton 8, PTM 28760, Tres Cantos, Madrid, Spain.
    Petroff, P.M.
    Materials Department, University of California, Santa Barbara, CA 93106, United States.
    Enhancement of the photoluminescence intensity of a single InAs/GaAs quantum dot by separate generation of electrons and holes2006In: Physics of the solid state, ISSN 1063-7834, E-ISSN 1090-6460, Vol. 48, no 10, p. 1993-1999Article in journal (Refereed)
    Abstract [en]

    It is demonstrated that the microphotoluminescence (µPL) spectrum of a single InAs/GaAs self-assembled quantum dot (QD) undergoes considerable changes when the primary laser excitation is complemented with an additional infrared laser. The primary laser, tuned slightly below the GaAs band gap, provides electron-hole pairs in the wetting layer (WL), as well as excess free electrons from ionized shallow acceptors in the GaAs barriers. An additional IR laser with a fixed energy well below the QD ground state transition generates excess free holes from deep levels in GaAs. The excess electron and hole will experience diffusion separately, due to the time separation between the two events of their generation, to eventually become captured into the QD. Although the generation rates of excess carries are much lower than that of the electron-hole pair generation in the WL, they considerably influence the QD emission at low temperatures. The integrated PL intensity increases by several times as compared to single-laser excitation, and the QD exciton spectrum is redistributed in favor of a more neutral charge configuration. The dependence of the observed phenomenon on the powers of the two lasers and the temperature has been studied and is consistent with the model proposed. The concept of dual excitation could be successfully applied to different low-dimensional semiconductor structures in order to manipulate their charge state and emission intensity. © Nauka/Interperiodica 2006.

  • 26.
    Dufåker, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Fredrik, Karlsson
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Mereni, L O.
    National University of Ireland University of Coll Cork, Ireland .
    Dimastrodonato, V
    National University of Ireland University of Coll Cork, Ireland .
    Juska, G
    National University of Ireland University of Coll Cork, Ireland .
    Pelucchi, E
    National University of Ireland University of Coll Cork, Ireland .
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Evidence of nonadiabatic exciton-phonon interaction probed by second-order LO-phonon replicas of single quantum dots2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 8Article in journal (Refereed)
    Abstract [en]

    In this experimental study of single InGaAs/GaAs quantum dots (QDs) the photoluminescence intensity of the second order LO-phonon replica of the excitonic interband recombination was measured along with the intensities of the first and zeroth orders. The results show that the intensity of the second-order replica is three to four times stronger than expected from the adiabatic Huang-Rhys theory, indicating that the neglected nonadiabaticity plays an important role for the understanding of the exciton-phonon coupling in QDs.

  • 27.
    Dufåker, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Dimastrodonato, V
    Tyndall National Institute, University College Cork, Ireland.
    O Mereni, L
    Tyndall National Institute, University College Cork, Ireland.
    Sernelius, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Pelucchi, E
    Tyndall National Institute, University College Cork, Ireland.
    Phonon replicas of charged and neutral exciton complexes in single quantum dots2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, no 20Article in journal (Refereed)
    Abstract [en]

    The longitudinal-optical (LO)-phonon coupling is experimentally examined by the optical decay of various charged and neutral exciton species in single quantum dots, and the related Huang-Rhys parameters are extracted. A positive trion exhibits significantly weaker LO-phonon replicas in the photoluminescence spectrum than the neutral and negatively charged species. Model computations show that the strength of the replicas is determined by the Coulomb interactions between electrons and holes, which modify the localization of the envelope wave functions and the net charge distribution.

  • 28.
    Dufåker, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Sernelius, Bo
    Linköping University.
    Pelucchi, E.
    Cork Univ. Ireland.
    Phonon Coupling of Exciton Complexes in Single InGaAs/AlGaAs Quantum Dots2010Conference paper (Refereed)
  • 29.
    Dufåker, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Karlsson, K. Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Mereni, L. O.
    Epitaxy and Physics of Nanostructures, Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Dimastrodonato, V.
    Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Juska, G.
    Tyndall National Institute, University College Cork, Ireland.
    Pelucchi, E.
    Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Quantum dot asymmetry and the nature of excited hole states probed by the doubly positively charged exciton X2+2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, no 4Article in journal (Refereed)
    Abstract [en]

    In this experimental and theoretical study, it was found that the emission pattern of the doubly positively charged exciton complex X2+ strongly depends on the nature of the involved excited hole states as well as the quantum dot symmetry. The two-hole system in the final state of the X2+ recombination for the investigated high-symmetry pyramidal InGaAs quantum dots does not exhibit the singlet-tripletlike arrangement previously observed for the two-electron counterpart. Instead, the final states exhibit two true doublets, in accordance with group-theoretical predictions. Asymmetry is manifested in the photoluminescence spectra of X2+ by a significant splitting of one doublet, which is a spectral feature exhibited to some degree by all of the measured quantum dots. The analysis demonstrates that an external magnetic field elevates the symmetry of the quantum dots. This work highlights the exciton complex X2+ as a very sensitive probe of the quantum dot shape as well as the nature of the involved quantum states. Thus, its spectral features are very suitable for an efficient uninvasive postgrowth symmetry characterization of quantum dots.

  • 30.
    Dufåker, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Mereni, L. O.
    Tyndall National Institute, University College Cork, Ireland.
    Karlsson, Fredrik K.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Dimastrodonato, V.
    Tyndall National Institute, University College Cork, Ireland.
    Juska, G.
    Tyndall National Institute, University College Cork, Ireland.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Pelucchi, E.
    Tyndall National Institute, University College Cork, Ireland.
    Exciton-phonon coupling in single quantum dots with different barriers2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 25, p. 251911-Article in journal (Refereed)
    Abstract [en]

    The coupling between longitudinal-optical (LO) phonons and neutral excitons in two different kinds of InGaAs pyramidal quantum dots embedded in either AlGaAs or GaAs barriers is experimentally examined. We find a slightly weaker exciton-LO-phonon coupling and increased linewidth of the phonon replicas for the quantum dots with GaAs barriers compared to the ones with AlGaAs barriers. These results, combined with the fact that the LO-phonon energy of the exciton is the same for both kinds of dots, are taken as evidence that the excitons mainly couple to LO-phonons within the QDs.

  • 31.
    Dupertuis, M A
    et al.
    Ecole Polytech Fed Lausanne.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Oberli, D Y
    Ecole Polytech Fed Lausanne.
    Pelucchi, E
    Ecole Polytech Fed Lausanne.
    Rudra, A
    Ecole Polytech Fed Lausanne.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kapon, E
    Ecole Polytech Fed Lausanne.
    Symmetries and the Polarized Optical Spectra of Exciton Complexes in Quantum Dots2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107, no 12, p. 127403-Article in journal (Refereed)
    Abstract [en]

    A systematic and simple theoretical approach is proposed to analyze true degeneracies and polarized decay patterns of exciton complexes in semiconductor quantum dots. The results provide reliable spectral signatures for efficient symmetry characterization, and predict original features for low C(2 nu) and high C(3 nu) symmetries. Excellent agreement with single quantum dot spectroscopy of real pyramidal InGaAs/AlGaAs quantum dots grown along [111] is demonstrated. The high sensitivity of biexciton quantum states to exact high symmetry can be turned into an efficient uninvasive postgrowth selection procedure for quantum entanglement applications.

  • 32.
    Elfving, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Larsson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Hansson, Göran V.
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Ni, Wei-Xin
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Efficient near infrared Si/Ge quantum dot photodetector based on a heterojunction bipolar transistor2003In: Material Research Society Symposium Proceedings, 2003, Vol. 770Conference paper (Refereed)
  • 33.
    Eriksson, Martin. O.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, K. Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    The Dynamics of Charged and Neutral Excitons in an InGaN Quantum Dot on a GaN PyramidManuscript (preprint) (Other academic)
    Abstract [en]

    The neutral (X0) and negatively charged excitons (X-) in an InGaN QD on a GaN pyramid is studied by the timeintegrated micro-photoluminescence (μPL) and time-resolved micro-photoluminescence (TRμPL) microcopies. Both X0 and X- exhibit mono-exponential decay curves with fitted lifetimes of 310 and 140 ps, respectively. Neither energy shifts nor changes in the life times X0 and X- with increasing excitation power were observed, indicating the QD is small and free from the quantum confine Stark effect. The TRμPL is not only a powerful technique for studying the dynamics of exciton in QDXs, but also for the identification of exciton complexes in QDs.

  • 34.
    Esmaeili, M
    et al.
    Islam Azad University.
    Gholami, M
    Islam Azad University.
    Haratizadeh, H
    Shahrood University of Technology.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Kamiyama, S
    Meijo University.
    Amano, H
    Meijo University.
    Akasaki, I
    Meijo University.
    Experimental and theoretical investigations of optical properties of GaN/AlGaN MQW nanostructures. Impact of built-in polarization fields2009In: OPTO-ELECTRONICS REVIEW, ISSN 1230-3402, Vol. 17, no 4, p. 293-299Article in journal (Refereed)
    Abstract [en]

    We report the results from detailed optical spectroscopy from MOCVD grown GaN/AlGaN multiple quantum wells (MQWs), as opposed to most previous studies where MBE was employed by means of photoluminescence (PL) technique. In this paper we will present theoretical and experimental results demonstrating how polarization induced electric fields and bound interface charges in GaN/AlGaN MQWs affect the emission peak energy, PL line shape, as well as the emission line width. Theoretically estimated fields in this work are consistent with experimental data. Transition energy of the heavy hole and electron ground state Ee-hh in GaN/AlGaN MQWs were calculated and it is found that it stays in good agreement with the experimental data.

  • 35. Esmaeili, M.
    et al.
    Harati Zadeh, Hamid
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Paskov, Plamen
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iwaya, M.
    Kamiyama, S.
    Amano, H.
    Akasaki, I
    Photoluminescence study of MOCVD-grown GaN/AlGaN MQW nanostructures: Influence of Al composition and Si doping2007In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, no 2Article in journal (Refereed)
    Abstract [en]

    A detailed study of low-temperature photoluminescence (PL) in GaN/AlGaN multiple quantum well (MQW) nanostructures has been reported. We have investigated the effect of Si doping and Al content on PL spectra and PL decay time of these structures. The temperature dependence of radiative as well as non-radiative lifetimes have been evaluated between 2K and room temperature for different Si doping. We found that radiative recombination at higher temperatures even up to RT is stronger in the doped sample, compared to the undoped one. Hole localization in GaN/AlGaN MQWs with different compositions of Al is demonstrated via PL transient decay times and LO phonon coupling. It is found that there is an increasing of the decay time at the PL peak emission with increasing Al composition. For the undoped sample, a non-exponential PL decay behaviour at 2K is attributed to localized exciton recombination. A slight upshift in QWs PL peak with increasing Al composition is observed, which is counteracted by the expected rise of the internal QW electric field with increasing Al. The localization energies have been evaluated by studying the variation of the QW emission versus temperature and we found out that the localization energy increases with increasing Al composition. © IOP Publishing Ltd.

  • 36. Esmaeili, M.
    et al.
    Sabooni, M.
    Islam Azad Univ, Dept Phys, Shahrood Branch, Shahrood, Iran.
    Haratizadeh, H.
    Shahrood Univ Technol, Dept Phys, Shahrood, Iran.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kamiyama, S.
    Meijo Univ, Dept Elect & Elect Engn, Tempaku Ku, Nagoya, Aichi 468, Japan.
    Iwaya, M.
    Meijo Univ, Dept Elect & Elect Engn, Tempaku Ku, Nagoya, Aichi 468, Japan.
    Optical properties of GaN/AlGaN QW nanostructures with different well and barrier widths2007In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 19, no 35Article in journal (Refereed)
    Abstract [en]

    Optical properties of wurtzite AlGaN/GaN quantum well (QW) structures grown by molecular-beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) on c-plane sapphire substrates have been investigated by means of photoluminescence (PL) and time-resolved photoluminescence (TRPL) at low temperature. The PL spectra exhibit a blue-shifted emission of GaN/AlGaN QW nanostructures by decreasing the barrier width, in contrast to the arsenide system (Pabla A S et al 1993 Appl. Phys. Lett. 63 752). This behavior is attributed to a redistribution across the samples of the huge built-in electric field (several hundreds of kV cm(-1)) induced by the polarization difference between wells and barriers. The trend of the barrier width dependence of the internal polarization field is reproduced by using simple electrostatic arguments. In addition, the effect of well width variation on the optical transition and decay time of GaN multiple quantum wells (MQWs) have been investigated, and it has been shown that the screening of the piezoelectric field and the electron-hole separation are strongly dependent on the well thickness and have a profound effect on the optical properties of the GaN/AlGaN MQWs. The time-resolved PL spectra of 3 nm well MQWs reveal that the spectral peak position shifts toward lower energies as the decay time increases and becomes red-shifted at longer decay times.

  • 37.
    Gholami, M
    et al.
    Islam Azad University.
    Esmaeili, M
    Islam Azad University.
    Haratizadeh, H
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Hammar, M
    Royal Institute Technology KTH.
    Evaluation of optical quality and properties of Ga0.64In0.36N0.006As0.994 lattice matched to GaAs by using photoluminescence spectroscopy2009In: OPTO-ELECTRONICS REVIEW, ISSN 1230-3402, Vol. 17, no 3, p. 260-264Article in journal (Refereed)
    Abstract [en]

    We have investigated optical properties of Ga0.64In0.36N0.006As0.994/GaAs single quantum-well structures using photoluminescence technique. We have found that nitrogen creates potential fluctuations in the InGaNAs structures, so it is the cause of trap centres in these structures and leads to localized excitons recombination dynamics. The near-band edge PL at 2 K exhibited a blueshift with an increase in excitation intensity of a sample but there is not such a shift in the PL peak position energy of same sample at 150 K. It has been found that PL spectra have a large full width at half maximum (FWHM) value at 2 K. These results are discussed in terms of carrier localization. Additionally, our results suggest decreasing PL integrated intensity in this structure, possibly due to non-radiative recombination. It has been shown that thermal annealing reduces the local strain created by nitrogen. By annealing process, a blue shifted emission can be observed.

  • 38.
    Gholami, M.
    et al.
    Physics Department, Shahrood University of Technology, PO Box 316, 3619995161, Shahrood, Iran, Department of Science, Islamic Azad University, Damghan Branch, Damghan, Iran.
    Haratizadeh, H.
    Physics Department, Shahrood University of Technology, PO Box 316, 3619995161, Shahrood, Iran, Department of Physics, Chemistry and Biology, Linkoping University, SE-581 581 83 Linkoping, Sweden.
    Esmaeili, M.
    Physics Department, Shahrood University of Technology, PO Box 316, 3619995161, Shahrood, Iran, Department of Science, Islamic Azad University, Damghan Branch, Damghan, Iran.
    Amiri, R.
    Physics Department, Shahrood University of Technology, PO Box 316, 3619995161, Shahrood, Iran.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Hammar, M.
    Department of Microelectronics and Applied Physics, School of Information and Communication Technology, Royal Institute of Technology (KTH), 16440 Kista-Stocholm, Sweden.
    Alternation of band gap and localization of excitons in InGaNAs nanostructures with low nitrogen content2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 31, p. 315705-Article in journal (Refereed)
    Abstract [en]

    Continuous wave photoluminescence (cw PL) spectroscopy has been used to study the optical properties of a set of InGaNAs epilayers and single quantum wells with nitrogen concentration less than a few per cent at different temperatures and different excitation powers. We found that nitrogen has a critical role on the emission light of InGaNAs nanostructures and the recombination mechanism. The incorporation of a few per cent of nitrogen leads to shrinkage of the InGaNAs band gap. The physical origin of such band gap reduction has been investigated both experimentally and theoretically by using a band anticrossing model. We have found that localization of excitons that have been caused by incorporation of a few per cent of nitrogen in these structures is the main explanation of such anomalous behavior observed in the low-temperature photoluminescence spectra of these nanostructures. The localization energies of carriers have been evaluated by studying the variation of the quantum well (QW) emission versus temperature, and it was found that the localization energy increases with increasing nitrogen composition. Our data also show that, with increasing excitation intensity, the PL peak position moves to higher energies (blue shift) due to the filling of localized states and capture centers for excitons by photo-generated carriers. © IOP Publishing Ltd.

  • 39. Gomes, P F
    et al.
    Cerdeira, F
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Elfving, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Madureira, J R
    García-Cristóbal, A
    Large optical emission blue shift in Ge/Si quantum dots under external biaxial strain2008In: ICPS 29th International Conference on the Physics of Semiconductors,2008, 2008Conference paper (Refereed)
  • 40. Gomes, P.F.
    et al.
    Gomes, P.F.
    Iikawa, F.
    Iikawa, F.
    Cerdeira, F.
    Cerdeira, F.
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Elfving, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Elfving, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Size dependent spatial direct and indirect transitions in Ge/Si QDs2007In: The 6th International Conference on Low Dimensional Structures and Devices,2007, 2007Conference paper (Refereed)
  • 41.
    Gomes, P.F.
    et al.
    Intituto de Física Gleb Wataghin, Unicamp, CP 6165, Campinas, São Paulo 13083-970, Brazil.
    Iikawa, F.
    Intituto de Física Gleb Wataghin, Unicamp, CP 6165, Campinas, São Paulo 13083-970, Brazil.
    Cerdeira, F.
    Intituto de Física Gleb Wataghin, Unicamp, CP 6165, Campinas, São Paulo 13083-970, Brazil.
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Elfving, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Type-I optical emissions in GeSi quantum dots2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 5Article in journal (Refereed)
    Abstract [en]

    The authors studied the optical emission of GeSi quantum dots under externally applied biaxial stress using samples grown with different temperatures varying from 430 to 700 °C. The optical emission energy of samples grown at low temperatures is rather insensitive to the applied external stress, consistent with the type-II band alignment. However, for samples grown at high temperatures we observed a large blueshift, which suggests type-I alignment. The result implies that recombination strength can be controlled by the growth temperature, which can be useful for optical device applications. © 2007 American Institute of Physics.

  • 42.
    Harati Zadeh, Hamid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Sernelius, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Iwaya, M
    Kamiyama, S
    Amano, H
    Akasaki, I
    Photoluminescence study of Si-doped GaN/Al0.07Ga0.93N multiple quantum wells with different dopant position2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, no 25, p. 5071-5073Article in journal (Refereed)
    Abstract [en]

    The Si-doped GaN/Al0.07Ga0.93N multiple quantum wells (MQW) were investigated, using photoluminescence (PL) and time-resolved (PL) measurements. The influence of Si doping on the emission energy and recombination dynamics of the MWQs were also investigated, with different dopant position in the wells. It was observed that the redshifted emission of the MQWs was attributed to the self-energy shift of the electron states due to the correlated motion of the electrons exposed to the fluctuating potential of the donor ions. It was also observed that the PL decay time of the sample was ∼760 ps, at low temperature.

  • 43.
    Harati Zadeh, Hamid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Amano, H.
    Akasaki, I.
    Optical Studies of Wide Band Gap III-Nitride Semiconductor Quantum Wells and Superlattices2006In: European Materials Research Society E-MRS fall meeting 2006,2006, 2006Conference paper (Other academic)
    Abstract [en]

       

  • 44.
    Harati Zadeh, Hamid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Valcheva, E
    Iwaya, M
    Kamiyama, S
    Amano, H
    Akasaki, I
    Optical observation of discrete well width fluctuations in wide band gap III-nitride quantum wells2007In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 244, no 5, p. 1727-1734Article in journal (Refereed)
    Abstract [en]

    A detailed observation of discrete well width fluctuations via localized excitons in the photoluminescence (PL) spectra of MOCVD-grown undoped GaN/Al0.07Ga0.93 N multiple quantum wells (MQWs) has been reported. Doublet excitonic features with a distance varying between 10 and 25 meV for different well widths (1.5 to 4.5 nm) are observed in the PL spectra. They are explained in terms of discrete well width variations by one c-lattice parameter, i.e. two GaN monolayers. By mapping the PL measurements across the samples with different excitation spot size, it is shown that the extension of areas with a constant well width is less than 1 μm2. TEM pictures give evidence of interface roughness, although the contrast is weak at this low Al composition. In addition we observe a long-range variation of the PL peak position across the sample, interpreted as a fluctuation in Al composition in the barriers. The residual broadening of an excitonic peak (apart from the splitting related to well width fluctuations) is about 10 meV, somewhat larger for larger well widths, and is mainly ascribed to hole localisation potentials in the QWs. Additional broadening occurs in the MQWs due to inequivalent properties of each QW within the excitation spot. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.

  • 45.
    Harati Zadeh, Hamid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kamiyama, S.
    Iwaya, M.
    Amano, H.
    Akasaki, I.
    Effect of n-type modulation doping on the photoluminescence of GaN/Al0.07Ga0.93N multiple quantum wells2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 80, no 8, p. 1373-Article in journal (Refereed)
    Abstract [en]

    [No abstract available]

  • 46.
    Harati Zadeh, Hamid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kamiyama, S.
    Iwaya, M.
    Amano, H.
    Akasaki, I.
    Photoluminescence study of Si doped GaN/AlGaN multi quantum wells2003In: ICPS 2002,2002, 2003, p. D-109-Conference paper (Refereed)
  • 47.
    Harati Zadeh, Hamid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kamiyama, S.
    Iwaya, M.
    Amano, H.
    Akasaki, I.
    Photoluminescence study of Si doped GaN/GaN/Al0.07Ga0.93N multi quantum wells2002In: NANO-7/ECOSS-21,2002, 2002, p. 13-Conference paper (Other academic)
  • 48.
    Harati Zadeh, Hamid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kamiyama, S.
    Iwaya, M.
    Amano, H.
    Akasaki, I.
    The influence of Si-donor doping on the exciton localization in modulation- doped GaN/AlGaN multi quantum wells2002In: 14th Indium Phosphide and Related Materials Conference IPRM 2002,2002, 2002, p. 495-Conference paper (Refereed)
  • 49. Haratizadeh, H.
    et al.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kamiyama, S.
    Department of Electrical Engineering, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, Japan.
    Iwaya, M.
    Department of Electrical Engineering, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, Japan.
    Amano, H.
    Department of Electrical Engineering, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, Japan.
    Akasaki, I.
    Department of Electrical Engineering, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, Japan.
    Time resolved photoluminescence study of Si modulation doped GaN/Al 0.07Ga0.93N multiple quantum wells2004In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 241, no 5, p. 1124-1133Article in journal (Refereed)
    Abstract [en]

    The effects of the Si doping level on the recombination dynamics and carrier (exciton) localization in modulation doped GaN/Al0.07Ga 0.93N multiple-quantum-well (MQW) structures were studied by means of photoluminescence (PL) and time-resolved PL measurements. All samples with different doping levels show a QW emission which is blue shifted with respect to the 3.48 eV PL peak from the GaN buffer layer. The decay time at the peak position remains nearly constant in the range of 320-420 ps at 2 K for all doping levels. For the undoped and low-doped samples (3 × 1018 cm-3), which have less free electrons in the QWs, a non-exponential PL decay behaviour at 2 K is attributed to localized exciton recombination. The more highly doped samples (5 × 1018 cm-3 to 10 20 cm-3) show almost exponential decay curves at 2 K, suggesting the recombination of free electrons and localized holes. This localization effect appears even at high electron concentrations to cancel the expected lowering of the radiative lifetime with doping at 2 K, such a lowering is clearly observed at elevated temperatures for the highly doped samples, however. The internal polarization-induced fields of the medium and highly-doped samples are partly screened by the electrons originating from the doping in the barriers. Only the PL peak of the undoped and low-doped samples shows a redshift with time delay, related to the photogenerated carriers. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 50.
    Hoglund, L
    et al.
    Acreo AB, S-16440 Kista, Sweden .
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Pettersson, H
    Halmstad University, Centre Appl Math and Phys, S-30118 Halmstad, Sweden Lund University, Solid State Phys and Nanometer Struct Consortium, S-22100 Lund, Sweden .
    Asplund, C
    IRnova, S-16440 Kista, Sweden .
    Wang, Q
    Acreo AB, S-16440 Kista, Sweden .
    Almqvist, S
    Acreo AB, S-16440 Kista, Sweden .
    Malm, H
    IRnova, S-16440 Kista, Sweden .
    Petrini, E
    Acreo AB, S-16440 Kista, Sweden .
    Andersson, J Y
    Acreo AB, S-16440 Kista, Sweden .
    Selective optical doping to predict the performance and reveal the origin of photocurrent peaks in quantum dots-in-a-well infrared photodetectors2009In: INFRARED PHYSICS and TECHNOLOGY, ISSN 1350-4495, Vol. 52, no 6, p. 272-275Article in journal (Refereed)
    Abstract [en]

    Resonant optical pumping across the band gap was used as artificial doping in InAs/In0.15Ga0.85As/GaAs quantum dots-in-a-well infrared photodetectors. Through efficient filling of the quantum dot energy levels by simultaneous optical pumping into the ground states and the excited states of the quantum dots, the response was increased by a factor of 10. Low temperature photocurrent peaks observed at 120 and 148 meV were identified as intersubband transitions emanating from the quantum dot ground state and the quantum dot excited state, respectively by a selective increase of the electron population in the different quantum dot energy levels.

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