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Wang, Xingjun
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Publications (10 of 65) Show all publications
Stehr, J. E., Wang, X., Filippov, S., Pearton, S. J., Gueorguiev Ivanov, I., Chen, W. & Buyanova, I. (2013). Defects in N, O and N, Zn implanted ZnO bulk crystals. Journal of Applied Physics, 113(10), 103509
Open this publication in new window or tab >>Defects in N, O and N, Zn implanted ZnO bulk crystals
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2013 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 10, p. 103509-Article in journal (Refereed) Published
Abstract [en]

Comprehensive characterization of defects formed in bulk ZnO single crystals co-implanted with N and Zn as well as N and O atoms is performed by means of optically detected magnetic resonance (ODMR) complemented by Raman and photoluminescence (PL) spectroscopies. It is shown that in addition to intrinsic defects such as Zn vacancies and Zn interstitials, several N-related defects are formed in the implanted ZnO. The prevailed configuration of the defects is found to depend on the choices of the co-implants and also the chosen annealing ambient. Specifically, co-implantation with O leads to the formation of (i) defects responsible for local vibrational modes at 277, 511, and 581 cm−1; (ii) a N-related acceptor with the binding energy of 160 ± 40 meV that is involved in the donor-acceptor pair emission at 3.23 eV; and (iii) a deep donor and a deep NO acceptor revealed from ODMR. Activation of the latter defects is found to require post-implantation annealing in nitrogen ambient. None of these defects are detected when N is co-implanted with Zn. Under these conditions, the dominant N-induced defects include a deep center responsible for the 3.3128 eV PL line, as well as an acceptor center of unknown origin revealed by ODMR. Formation mechanisms of the studied defects and their role in carrier recombination are discussed.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-91343 (URN)10.1063/1.4795261 (DOI)000316565600020 ()
Note

Funding Agencies|Swedish Research Council|621-2010-3971|

Available from: 2013-04-22 Created: 2013-04-22 Last updated: 2018-04-25Bibliographically approved
Puttisong, Y., Wang, X., Buyanova, I., Ptak, A. J., Tu, C. W., Geelhaar, L., . . . Chen, W. (2012). Defect-enabled Room-temperature Spin Functionality in Ga(In)NAs. Paper presented at 31'st International Conference on the Physics of Semiconductors (ICPS 2012), July 29-August 3, Zurich, Switzerland.
Open this publication in new window or tab >>Defect-enabled Room-temperature Spin Functionality in Ga(In)NAs
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2012 (English)Conference paper, Published 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.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-80758 (URN)
Conference
31'st International Conference on the Physics of Semiconductors (ICPS 2012), July 29-August 3, Zurich, Switzerland
Available from: 2012-08-29 Created: 2012-08-29 Last updated: 2017-03-27
Wang, X., Chen, W., Ren, F., Pearton, S. & Buyanova, I. (2012). Effects of P implantation and post-implantation annealing on defect formation in ZnO. Journal of Applied Physics, 111(4), 043520
Open this publication in new window or tab >>Effects of P implantation and post-implantation annealing on defect formation in ZnO
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2012 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 4, p. 043520-Article in journal (Refereed) Published
Abstract [en]

Photoluminescence (PL) and optically detected magnetic resonance (ODMR) techniques are utilized to examine the effects of P implantation and post-implantation annealing on defect formation in ZnO single crystals. From ODMR, the main defects created by ion implantation include oxygen and zinc vacancies as a well as a deep donor labeled as PD. The formation of the PD defect is likely promoted by the presence of P as it could only be detected in the P-containing ZnO. The V-O and PD centers are found to exhibit low thermal stability and can be annealed out at 800 degrees C. On the other hand, a new set of defects, such as Z, T, and D* centers, is detected after annealing. Based on measured spectral dependences of the ODMR signals, the V-O, V-Zn, and PD centers are shown to participate in spin-dependent recombination processes related to red emissions, whereas the Z, T, and D* centers are involved in radiative recombination over a wide spectral range of 1.55-2.5 eV. From the PL measurements, combined effects of implantation and annealing also lead to appearance of a new PL band peaking at similar to 3.156 eV, likely due to donor-acceptor-pair recombination. The formation of the involved deep acceptor is concluded to be facilitated by the presence of P.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-76194 (URN)10.1063/1.3687919 (DOI)000300948600037 ()
Note

Funding Agencies|Swedish Research Council|621-2010-3971|National Basic Research Program of China|2011CB925604|

Available from: 2012-03-31 Created: 2012-03-30 Last updated: 2018-10-08
Dagnelund, D., Wang, X., Tu, C., Polimeni, A., Capizzi, M., Buyanova, I. A. & Chen, W. (2011). Activation of defects in GaNP by low-energy hydrogen treatment. In: Abstract book of the 9th Int. Conf. on Nitride Semiconductors, Glasgow, UK. Paper presented at 9th Int. Conf. on Nitride Semiconductors, Glasgow, UK, July 10-15 2011 (pp. PC3.36).
Open this publication in new window or tab >>Activation of defects in GaNP by low-energy hydrogen treatment
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2011 (English)In: Abstract book of the 9th Int. Conf. on Nitride Semiconductors, Glasgow, UK, 2011, p. PC3.36-Conference paper, Published paper (Other academic)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-73855 (URN)
Conference
9th Int. Conf. on Nitride Semiconductors, Glasgow, UK, July 10-15 2011
Available from: 2012-01-15 Created: 2012-01-15 Last updated: 2017-03-27
Dagnelund, D., Wang, X., Tu, C. W., Polimeni, A., Capizzi, M., Chen, W. & Buyanova, I. (2011). Effect of postgrowth hydrogen treatment on defects in GaNP. APPLIED PHYSICS LETTERS, 98(14), 141920
Open this publication in new window or tab >>Effect of postgrowth hydrogen treatment on defects in GaNP
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2011 (English)In: APPLIED PHYSICS LETTERS, ISSN 0003-6951, Vol. 98, no 14, p. 141920-Article in journal (Refereed) Published
Abstract [en]

Effect of postgrowth hydrogen treatment on defects and their role in carrier recombination in GaNP alloys is examined by photoluminescence (PL) and optically detected magnetic resonance. We present direct experimental evidence for effective activation of several defects by low-energy subthreshold hydrogen treatment (andlt;= 100 eV H ions). Among them, two defect complexes are identified to contain a Ga interstitial. Possible mechanisms for the H-induced defect activation and creation are discussed. Carrier recombination via these defects is shown to efficiently compete with the near band-edge PL, explaining the observed degraded optical quality of the alloys after the H treatment.

Place, publisher, year, edition, pages
American Institute of Physics, 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-67843 (URN)10.1063/1.3576920 (DOI)000289297800035 ()
Note
Original Publication: Daniel Dagnelund, Xingjun Wang, C W Tu, A Polimeni, M Capizzi, Weimin Chen and Irina Buyanova, Effect of postgrowth hydrogen treatment on defects in GaNP, 2011, APPLIED PHYSICS LETTERS, (98), 14, 141920. http://dx.doi.org/10.1063/1.3576920 Copyright: American Institute of Physics http://www.aip.org/ Available from: 2011-04-29 Created: 2011-04-29 Last updated: 2018-10-08
Wang, X., Puttisong, Y., Tu, C., Ptak, A. J., Kalevich, V., Egorov, A., . . . Chen, W. (2011). Engineering spin-dependent carrier recombination processes in Ga(In)NAs for optoelectronic and photovoltaic applications. In: Abstract Book of  the Int. Conf. on Fundamental Optical Processes in Semiconductors, Lake Junaluska, USA. Paper presented at the Int. Conf. on Fundamental Optical Processes in Semiconductors, Lake Junaluska, USA, Aug.1-5 2011 (pp. PB3.).
Open this publication in new window or tab >>Engineering spin-dependent carrier recombination processes in Ga(In)NAs for optoelectronic and photovoltaic applications
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2011 (English)In: Abstract Book of  the Int. Conf. on Fundamental Optical Processes in Semiconductors, Lake Junaluska, USA, 2011, p. PB3.-Conference paper, Published paper (Other academic)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-73856 (URN)
Conference
the Int. Conf. on Fundamental Optical Processes in Semiconductors, Lake Junaluska, USA, Aug.1-5 2011
Available from: 2012-01-15 Created: 2012-01-15 Last updated: 2017-03-27
Puttisong, Y., Wang, X., Buyanova, I., Tu, C. W., Geelhaar, L., Riechert, H. & Chen, W. (2011). Room-temperature spin injection and spin loss across a GaNAs/GaAs interface. Applied Physics Letters, 98(1), 012112
Open this publication in new window or tab >>Room-temperature spin injection and spin loss across a GaNAs/GaAs interface
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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
Puttisong, Y., Wang, X., Buyanova, I. A., Tu, C., Geelhaar, L., Riechert, H. & Chen, W. (2011). Studies of spin loss during room-temperature spin injection across a GaNAs/GaAs interface. In: Abstract book of the 9th Int. Conf. on Nitride Semiconductors, Glasgow, UK. Paper presented at 9th Int. Conf. on Nitride Semiconductors, Glasgow, UK, July 10-15 2011 (pp. PC1.12).
Open this publication in new window or tab >>Studies of spin loss during room-temperature spin injection across a GaNAs/GaAs interface
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2011 (English)In: Abstract book of the 9th Int. Conf. on Nitride Semiconductors, Glasgow, UK, 2011, p. PC1.12-Conference paper, Published paper (Other academic)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-73854 (URN)
Conference
9th Int. Conf. on Nitride Semiconductors, Glasgow, UK, July 10-15 2011
Available from: 2012-01-15 Created: 2012-01-15 Last updated: 2017-03-27
Puttisong, Y., Wang, X., Buyanova, I., Carrere, H., Zhao, F., Balocchi, A., . . . Chen, W. (2010). Electron spin filtering by thin GaNAs/GaAs multiquantum wells. Applied Physics Letters, 96(5), 052104
Open this publication in new window or tab >>Electron spin filtering by thin GaNAs/GaAs multiquantum wells
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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
Dagnelund, D., Vorona, I. P., Vlasenko, L. S., Wang, X. J., Utsumi, A., Furukawa, Y., . . . Chen, W. M. (2010). Evidence for a phosphorus-related interfacial defect complex at a GaP/GaNP heterojunction. Physical Review B. Condensed Matter and Materials Physics, 81, 115334
Open this publication in new window or tab >>Evidence for a phosphorus-related interfacial defect complex at a GaP/GaNP heterojunction
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2010 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, p. 115334-Article in journal (Refereed) Published
Abstract [en]

Optically detected magnetic resonance (ODMR) studies of molecular beam epitaxial GaNP/GaP structures reveal presence of a P-related complex defect, evident from its resolved hyperfine interaction between an unpaired electronic spin (S=1/2) and a nuclear spin (I = ½) of a 31P atom. The principal axis of the defect is concluded to be along a <111> crystallographic direction from angular dependence of the ODMR spectrum, restricting the P atom (either a PGa antisite or a Pi interstitial) and its partner in the complex defect to be oriented along this direction. The principal values of the electronic g-tensor and hyperfine interaction tensor are determined as: g=2.013, g=2.002, and A=130´10-4 cm-1, A=330´10-4 cm-1, respectively. The interface nature of the defect is clearly manifested by the absence of the ODMR lines originating from two out of four equivalent <111> orientations. Defect formation is shown to be facilitated by nitrogen ion bombardment under non-equilibrium growth conditions and the defect is thermally stable upon post-growth thermal annealing.

Place, publisher, year, edition, pages
The American Physical Society, 2010
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-54721 (URN)10.1103/PhysRevB.81.115334 (DOI)000276248800111 ()
Note

Original Publication: Daniel Dagnelund, I. P Vorona, L. S. Vlasenko, X. J. Wang, A. Utsumi, Y. Furukawa, A. Wakahara, H. Yonezu, I. A. Buyanova and W. M. Chen, Evidence for a phosphorus-related interfacial defect complex at a GaP/GaNP heterojunction, 2010, Physical Review B Condensed Matter, (81), , 115334. http://dx.doi.org/10.1103/PhysRevB.81.115334 Copyright: American Physical Society http://www.aps.org/

Available from: 2010-04-06 Created: 2010-04-06 Last updated: 2017-12-12
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