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  • 101.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Donor bound excitons involving a hole from the B valence band in ZnO: Time resolved and magneto-photoluminescence studies (vol 99, 091909, 2011)2012Other (Refereed)
    Abstract [en]

    n/a

  • 102.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dynamics of donor bound excitons in ZnO2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 12, p. 121103-Article in journal (Refereed)
    Abstract [en]

    Comprehensive time-resolved photoluminescence measurements are performed on shallow neutral donor bound excitons (D0Xs) in bulk ZnO. It is found that transients of the no-phonon D0X transitions (I6-I9 lines) are largely affected by excitation conditions and change from a bi-exponential decay with characteristic fast (τf) and slow (τs) time constants under above-bandgap excitation to a single exponential one, determined by τs, under two-photon excitation. The slow decay also dominates transients of longitudinal optical phonon-assisted and two-electron-satellite D0X transitions, and is attributed to “bulk” D0X lifetime. The fast component is tentatively suggested to represent effects of surface recombination.

  • 103.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Long delays of light in ZnO caused by exciton-polariton propagation2012In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 249, no 7, p. 1307-1311Article in journal (Refereed)
    Abstract [en]

    We study the propagation of exciton-polaritons through bulk ZnO using time-resolved photoluminescence (PL) complemented by time-of-flight measurements of laser pulses. When the photon energy approaches donor bound exciton resonances, substantial time delays in PL light propagation are observed which reach up to 210 ps for a 0.55 mm thick crystal. By comparing results from time-of-flight measurements performed using PL light and laser pulses, the observed delay is shown to be due to the formation of exciton-polaritons and their spectral dispersion. It is also shown that the main contribution to the slow-down effect arises from free exciton-polaritons, whereas bound exciton-polaritons become important only in close vicinity to the corresponding resonances.

  • 104.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Magneto-optical properties and dynamics of donor bound excitons involving a B valence band hole.2012Conference paper (Other academic)
  • 105.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Magneto-optical spectroscopy of donor bound excitons involving B valence band hole2012Conference paper (Other academic)
  • 106.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Realization of slow light in ZnO media2012Conference paper (Other academic)
  • 107.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Slowdown of light due to exciton-polariton propagation in ZnO2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 24, p. 245212-Article in journal (Refereed)
    Abstract [en]

    By employing time-of-flight spectroscopy, the group velocity of light propagating through bulk ZnO is demonstrated to dramatically decrease down to 2044 km/s when photon energy approaches the absorption edge of the material. The magnitude of this decrease is found to depend on light polarization. It is concluded that even though the slowdown is observed in the vicinity of donor bound exciton (BX) resonances, the effect is chiefly governed by dispersion of free exciton (FX) polaritons that propagate coherently via ballistic transport. Based on the experimentally determined spectral dependence of the polariton group velocity, the polariton dispersion is accurately determined.

  • 108.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Spin dynamics of isoelectronic bound excitons in ZnO2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 23, p. 235202-Article in journal (Refereed)
    Abstract [en]

    Time-resolved optical spin orientation is employed to study spin dynamics of I * and I-1* excitons bound to isoelectronic centers in bulk ZnO. It is found that spin orientation at the exciton ground state can be generated using resonant excitation via a higher lying exciton state located at about 4 meV from the ground state. Based on the performed rate equation analysis of the measured spin dynamics, characteristic times of subsequent hole, electron, and direct exciton spin flips in the exciton ground state are determined as being tau(s)(h) = 0.4 ns, tau(s)(e) greater than= 15 ns, and tau(s)(eh) greater than= 15 ns, respectively. This relatively slow spin relaxation of the isoelectronic bound excitons is attributed to combined effects of (i) weak e-h exchange interaction, (ii) restriction of the exciton movement due to its binding at the isoelectronic center, and (iii) suppressed spin-orbit coupling for the tightly bound hole.

  • 109.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Zeeman splitting and dynamics of an isoelectronic bound exciton near the band edge of ZnO2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 23Article in journal (Refereed)
    Abstract [en]

    Comprehensive time-resolved photoluminescence and magneto-optical measurements are performed on a bound exciton (BX) line peaking at 3.3621 eV (labeled as I*). Though the energy position of I* lies within the same energy range as that for donor bound exciton (DX) transitions, its behavior in an applied magnetic field is found to be distinctly different from that observed for DXs bound to either ionized or neutral donors. An exciton bound to an isoelectronic center with a hole-attractive local potential is shown to provide a satisfactory model that can account for all experimental results of the I* transition. DOI: 10.1103/PhysRevB.86.235205

  • 110.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Efficient upconversion of photoluminescence in bulk and nanorod ZnO2012Conference paper (Refereed)
  • 111.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Filippov, Stanislav
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Ishikawa, Fumitaro
    Ehime University, Japan.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Origin of radiative recombination and manifestations of localization effects in GaAs/GaNAs core/shell nanowires2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 25, p. 253106-Article in journal (Refereed)
    Abstract [en]

    Radiative carrier recombination processes in GaAs/GaNAs core/shell nanowires grown by molecular beam epitaxy on a Si substrate are systematically investigated by employing micro-photoluminescence (mu-PL) and mu-PL excitation (mu-PLE) measurements complemented by time-resolved PL spectroscopy. At low temperatures, alloy disorder is found to cause localization of photo-excited carriers leading to predominance of optical transitions from localized excitons (LE). Some of the local fluctuations in N composition are suggested to lead to strongly localized three-dimensional confining potential equivalent to that for quantum dots, based on the observation of sharp and discrete PL lines within the LE contour. The localization effects are found to have minor influence on PL spectra at room temperature due to thermal activation of the localized excitons to extended states. Under these conditions, photo-excited carrier lifetime is found to be governed by non-radiative recombination via surface states which is somewhat suppressed upon N incorporation. (C) 2014 AIP Publishing LLC.

  • 112.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Jansson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Filippov, Stanislav
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Ishikawa, Fumitaro
    Ehime University, Japan.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Core-shell carrier and exciton transfer in GaAs/GaNAs coaxial nanowires2016In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 34, no 4, p. 04J104-Article in journal (Refereed)
    Abstract [en]

    Comprehensive studies of GaAs/GaNAs coaxial nanowires grown on Si substrates are carried out by temperature-dependent photoluminescence (PL) and PL excitation, to evaluate effects of the shell formation on carrier recombination. The PL emission from the GaAs core is found to transform into a series of sharp PL lines upon radial growth of the GaNAs shell, pointing toward the formation of localization potentials in the core. This hampers carrier transfer at low temperatures from the core in spite of its wider bandgap. Carrier injection from the core to the optically active shell is found to become thermally activated at Tamp;gt;60 K, which implies that the localization potentials are rather shallow. (C) 2016 American Vacuum Society.

  • 113.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Jansson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Huang, Yuqing
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Ishikawa, Fumitaro
    Ehime University, Japan.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Dilute Nitride Nanowire Lasers Based on a GaAs/GaNAs Core/Shell Structure2017In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 3, p. 1775-1781Article in journal (Refereed)
    Abstract [en]

    Nanowire (NW) lasers operating in the near infrared spectral range are of significant technological importance for applications in telecommunications, sensing, and medical diagnostics. So far, lasing within this spectral range has been achieved using GaAs/AlGaAs, GaAs/GaAsP, and InGaAs/GaAs core/shell NWs. Another promising III-V material, not yet explored in its lasing capacity, is the dilute nitride GaNAs. In this work, we demonstrate, for the first time, optically pumped lasing from the GaNAs shell of a single GaAs/GaNAs core/shell NW. The characteristic "S"-shaped pump power dependence of the lasing intensity, with the concomitant line width narrowing, is observed, which yields a threshold gain, g(th), of 3300 cm(-1) and a spontaneous emission coupling factor beta, of 0.045. The dominant lasing peak is identified to arise from the HE21b, cavity mode, as determined from its pronounced emission polarization along the NW axis combined with theoretical calculations of lasing threshold for guided modes inside the nanowire. Even without intentional pas sivation of the NW surface, the lasing emission can be sustained up to 150 K. This is facilitated by the improved surface quality due to nitrogen incorporation, which partly suppresses the surface-related nonradiative recombination centers via nitridation. Our work therefore represents the first step toward development of room-temperature infrared NW lasers based on dilute nitrides with extended tunability in the lasing wavelength.

  • 114.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Kyun Lee, Sun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dong, H X
    Fudan University.
    Sun, L
    Fudan University.
    Chen, Z H
    Fudan University.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    On the origin of suppression of free exciton no-phonon emission in ZnO tetrapods2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 3, p. 033108-Article in journal (Refereed)
    Abstract [en]

    Temperature dependent photoluminescence and cathodoluminescence (CL) spectroscopies are employed to investigate free exciton (FX) emissions in ZnO tetrapods. The intensity of the no-phonon line is found to be largely suppressed as compared with longitudinal optical phonon assisted transitions, in sharp contrast to bulk ZnO. From spatially resolved CL studies, this suppression is shown to strongly depend on structural morphology of the ZnO tetrapods and becomes most significant within areas with faceted surfaces. A model based on reabsorption due to multiple internal reflections in the vicinity of the FX resonance is suggested to account for the observed effect.

  • 115.
    Chen, Shula L
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Long delays of light in ZnO caused by exciton-polariton propagation2011In: Abstract Book of  the Int. Conf. on Fundamental Optical Processes in Semiconductors, Lake Junaluska, USA, 2011, p. PB2.-Conference paper (Other academic)
  • 116.
    Chen, Shula L.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Ishikawa, Fumitaro
    Graduate School of Science and Engineering, Ehime University, 790-8577 Matsuyama, Japan.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Suppression of non-radiative surface recombination by N incorporation in GaAs/GaNAs core/shell nanowires2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 11653Article in journal (Refereed)
    Abstract [en]

    III-V semiconductor nanowires (NWs) such as GaAs NWs form an interesting artificial materials system promising for applications in advanced optoelectronic and photonic devices, thanks to the advantages offered by the 1D architecture and the possibility to combine it with the main-stream silicon technology. Alloying of GaAs with nitrogen can further enhance performance and extend device functionality via band-structure and lattice engineering. However, due to a large surface-to-volume ratio, III-V NWs suffer from severe non-radiative carrier recombination at/near NWs surfaces that significantly degrades optical quality. Here we show that increasing nitrogen composition in novel GaAs/GaNAs core/shell NWs can strongly suppress the detrimental surface recombination. This conclusion is based on our experimental finding that lifetimes of photo-generated free excitons and free carriers increase with increasing N composition, as revealed from our time-resolved photoluminescence (PL) studies. This is accompanied by a sizable enhancement in the PL intensity of the GaAs/GaNAs core/shell NWs at room temperature. The observed N-induced suppression of the surface recombination is concluded to be a result of an N-induced modification of the surface states that are responsible for the nonradiative recombination. Our results, therefore, demonstrate the great potential of incorporating GaNAs in III-V NWs to achieve efficient nano-scale light emitters.

  • 117.
    Chen, Shula L
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Lee, Sun-Kyun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Cathodoluminescence studies of ZnO tetrapod structures2011In: Abstract Book of the 2nd nano Today Conference, Hawaii, USA, 2011, p. P1.24-Conference paper (Other academic)
  • 118.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Koteeswara Reddy, N.
    Gwangju Institute of Science and Technology, Republic of Korea.
    Tu, C. W.
    Gwangju Institute of Science and Technology, Republic of Korea.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Efficient upconvertion of photoluminescence via two-photon-absorption in bulk and nanorod ZnO2012In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 108, no 4, p. 919-924Article in journal (Refereed)
    Abstract [en]

    Efficient upconversion of photoluminescence from donor-bound excitons is revealed in bulk and nanorod ZnO. Based on excitation power-dependent PL measurements performed with different energies of excitation photons, two-photon absorption (TPA) and two-step TPA (TS-TPA) processes are concluded to be responsible for the upconversion. The TS-TPA process is found to occur via a defect/impurity (or defects/impurities) with an energy level (or levels) lying within 1.14–1.56 eV from one of the band edges, without involving photon recycling. One of the possible defect candidates could be VZn. A sharp energy threshold, different from that for the corresponding one-photon absorption, is observed for the TPA process and is explained in terms of selection rules for the involved optical transitions.

  • 119.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Applications of optically detected magnetic resonance in semiconductor layered structures2000In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 364, no 1, p. 45-52Article in journal (Refereed)
    Abstract [en]

    A short introduction is given on the physics, method, capabilities and limitations of the optically detected magnetic resonance (ODMR) technique. The advantages of the optical detection method in terms of sensitivity and of its direct probe in recombination processes, as compared with the traditional spin resonance technique, will be demonstrated. The importance of these advantages for the ODMR applications in semiconductor layered and quantum structures will be emphasized. The ability of the ODMR technique to provide important information on physical properties of semiconductor layered structures will be highlighted. These include chemical identification, electronic and geometric structure of both radiative and non-radiative defects, carrier recombination mechanism, electronic excitation, etc. Representative cases from CVD-SiC and MBE-Si/SiGe based layered structures will be discussed as examples. The most recent progress, on-going efforts and prospects in achieving unprecedentedly high spectral, time and spatial resolution of the ODMR technique will also be outlined.

  • 120.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Optically detected magnetic resonance1999In: Nordic EPR Group Workshop,1999, 1999Conference paper (Other academic)
  • 121.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Optically detected magnetic resonance of defects in semiconductors2013In: EPR of Free Radicals in Solids II: Trends in Methods and Applications / [ed] A. Lund and M. Shiotani, Dordrecht: Springer Netherlands, 2013, 2, p. 345-366Chapter in book (Other academic)
    Abstract [en]

    EPR of Free Radicals in Solids: Trends in Methods and Applications, 2nd ed. presents a critical two volume review of the methods and applications of EPR (ESR) for the study of free radical processes in solids. Emphasis is on the progress made in the developments in EPR technology, in the application of sophisticated matrix isolation techniques and in the advancement in quantitative EPR that have occurred since the 1st edition was published. Improvements have been made also at theoretical level, with the development of methods based on first principles and their application to the calculation of magnetic properties as well as in spectral simulations. EPR of Free Radicals in Solids II focuses on the trends in applications of experimental and theoretical methods to extract structural and dynamical properties of radicals and spin probes in solid matrices by continuous wave (CW) and pulsed techniques in nine chapters written by experts in the field. It examines the studies involving radiation- and photo-induced inorganic and organic radicals in inert matrices, the high-spin molecules and metal-based molecular clusters as well as the radical pro-cesses in photosynthesis. Recent advancements in environmental applications in-cluding measurements by myon resonance of radicals on surfaces and by quantitative EPR in dosimetry are outlined and the applications of optical detection in material research with much increased sensitivity reviewed. The potential use of EPR in quantum computing is considered in a newly written chapter. This new edition is aimed to experimentalists and theoreticians in research involving free radicals, as well as for students of advanced courses in physical chemis-try, chemical physics, materials science, biophysics, biochemistry and related fields.

  • 122.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Optically detected magnetic resonance of defects in semiconductors2003In: EPR of Free Radicals in Solids Trends in Methods and Applications / [ed] Anders Lund and Masaru Shiotani, AH Dordrecht, The Netherlands: Kluwer Academic Publishers , 2003, p. 601-626Chapter in book (Other academic)
    Abstract [en]

    EPR of Free Radicals in Solids: Trends in Methods and Applications presents methods and applications of modern EPR for the study of free radical processes in solids, which so far are only available in the journal literature. The first part of the book, covering trends in methods, contains experimentally oriented chapters on continuous wave and pulsed EPR techniques and special methods involving muon magnetic resonance and optical detection and theory for dynamic studies. New simulation schemes, including the influence of dynamics, are presented as well as advances in the calculation of hyperfine and electronic g-tensors. The second part of the book presents applications involving studies of radiation and photo-induced inorganic and organic radicals in inert matrices, including novel results of quantum effects in small radicals. High-spin molecules and complexes are also considered as well as radical processes in photosynthesis. Recent advances in EPR dosimetry are summarized.

  • 123.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Optically detected magnetic resonance of semiconductor thin films and layered structures2000In: Fourth International Conference on Thin Film Physics and Applications,2000, Proc. SPIE, Vol. 4086: SPIE , 2000, Vol. 4086, p. 44-Conference paper (Refereed)
    Abstract [en]

     The principle, capabilities, advantages and limitations of the optically detected magnetic resonance (ODMR) technique will be briefly described. The ability of the ODMR technique to provide important information on physical properties of semiconductor thin films and layered structures will be highlighted. These include chemical identification, electronic and geometric structures of defects, carrier recombinations, etc. The important role in providing valuable feedback for improvement of growth process and in engineering material properties for device applications will be demonstrated. Representative cases from Si/SiGe- and InP- based structures grown by molecular beam epitaxy will be discussed as examples. The most recent progress, on-going efforts and prospects in achieving unprecedently high spectral, time and spatial resolution of the ODMR technique, meeting the demands and challenges raised by the increasing miniaturization of future electronic and optoelectronic devices, will also be outlined.

  • 124.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Beyer, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Suraprapapich, S
    Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, USA .
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Spin properties of InAs/GaAs quantum dot structures relevant to room-temperature spintronics.2013Conference paper (Refereed)
  • 125.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Beyer, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Suraprapapich, S
    Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, USA .
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Spin properties of InAs/GaAs quantum dot structures relevant to room-temperature spintronics2013In: XXII International Materials Research Congress, 2013Conference paper (Refereed)
  • 126.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanov, A. V.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Lundström, Tim
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Bi, W. G.
    Zeng, Y. P.
    Tu, C. W.
    Transport properties of intrinsically and extrinsically modulation doped InP/InGaAs heterostructures1999In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T79, p. 103-105Article in journal (Refereed)
    Abstract [en]

     Transport properties in a new type of modulation doped InP/InGaAs systems, where the n-type doping is provided by intrinsic PIn-antisite defects rather than foreign impurities, are studied by Shubnikov-de-Haas (SdH) oscillations and low-field Hall effect measurements. A close comparison of transport properties is made between these intrinsically modulation doped structures with extrinsically doped structures, with the emphasis on two of the most important physical processes i.e. doping efficiency and scattering mechanism. It is found that the efficiency of the intrinsic modulation doping is at least as high as the extrinsic modulation doping. The mobilities of the two dimensional electron gas (2DEG) derived from Hall and SdH measurements are shown to be higher in the intrinsically doped structures as compared to the extrinsically doped structures. This is attributed to a reduced scattering of the 2DEG by the remote parent dopants, due to e.g. an increased screening of the scattering potential by the excess free electrons present in the intrinsic doping region due to auto-ionization of the PIn antisite.

  • 127.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Defect-enabled spin functionality: a new approach for room-temperature semiconductor spintronics2014In: Abstract Book of the 6th IEEE International Nanoelectronics Conference, 2014, p. 214-Conference paper (Other academic)
  • 128.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Defect-engineered spin functionality in a non-magnetic semiconductor.: Invited talk at the 3rd Nordic Workshop on Spintronics and Nanomagnetism, Varberg Kurort, April 22-25, 2012.2012Conference paper (Refereed)
  • 129.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Electron effective masses of dilute nitrides: Experiment2004In: Physics and Applications of Dilute Nitrides / [ed] Irina A. Buyanova and Weimin M. Chen, New York: Taylor & Francis , 2004, 1, p. 93-116Chapter in book (Other academic)
    Abstract [en]

    Since their development in the 1990s, it has been discovered that diluted nitrides have intriguing properties that are not only distinct from those of conventional semiconductor materials, but also are conducive to various applications in optoelectronics and photonics. The book examines these applications and presents a broad and in-depth look at the basic electronic and optical properties of diluted nitrides.

    The aim of Physics and Applications of Diluted Nitrides is to provide graduate students, researchers and engineers with a comprehensive overview of the present knowledge and future perspectives of diluted nitrides.

    Co-authored by a group of leading scientists in the field, this book brings the reader up to speed on the development and current state of diluted nitride applications, as well as the technologies to be developed in the near future.

  • 130.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology. Linköping University, The Tema Institute.
    Buyanova, IrinaLinköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology. Linköping University, The Tema Institute.
    Handbook of Spintronic Semiconductors2010Collection (editor) (Other academic)
    Abstract [en]

    Spintronics explores the spin degree of freedom of the electron to sense, store, process and transfer information in addition to the electron charge. Semiconductor spintronics promises to combine new spin enabling functionality with the present-day microelectronics and optoelectronics. It also opens the door to new generation of devices, and to the merging of electronics, photonics and magnetics. The success of spintronics relies on our ability to create and control spins. Among many obstacles, generation of electron spin polarization and coherence at room temperature is one of the most important as well as the most challenging issues, which has attracted intense research efforts during recent years. Significant progresses have been made both theoretically and experimentally, while many issues remain unresolved.

    This book provides an in-depth review of the rapidly developing field of spintronic semiconductors. It covers a broad range of topics, including growth and basic physical properties of diluted magnetic semiconductors based on II-VI, III-V and IV semiconductors, recent developments in theory and experimental techniques and potential device applications; its aim is to provide postgraduate students, researchers and engineers a comprehensive overview of our present knowledge and future perspectives of spintronic semiconductors.

  • 131.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Room-Temperature Defect-Enabled Spin Functionality in GaAs-Based Coumpound Semiconductors2014In: Program Book of the 226th Meeting of The Electrochemical Society, 2014, p. 127-Conference paper (Other academic)
  • 132.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Room-temperature Spin Generation and Detection in Semiconductor Nanostructures for Future Spintronics.2011In: Proc. 1st Annual World Congress of Nano-S&T, 2011, p. 116-Conference paper (Other academic)
  • 133.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Efficient room temperature spin filter based on a non-magnetic semiconductor2010Conference paper (Other academic)
  • 134.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Department of Thematic Studies. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Department of Thematic Studies. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Extraordinary Defect-enabled Spin Functionalities in Semiconductors (invited talk)Extraordinary Defect-enabled Spin Functionalities in Semiconductors2016In: Proc. of the 33rd Int. Conf. Phys. Semicond. (2017) in press, 2016Conference paper (Refereed)
  • 135.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Rudko, GY
    Mal'shukov, AG
    Chao, KA
    Toropov, AA
    Terent'ev, Y
    Sorokin, SV
    Lebedev, Alexander
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Ivanov, SV
    Kop'ev, PS
    Exciton spin relaxation in diluted magnetic semiconductor Zn1-xMnxSe/CdSe superlattices: Effect of spin splitting and role of longitudinal optical phonons2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 67, no 12Article in journal (Refereed)
    Abstract [en]

    Exciton spin relaxation in diluted magnetic semiconductor (DMS) structures based on ZnMnSe is closely examined as a function of exciton spin splitting in an external magnetic field. A drastic increase in spin relaxation is observed when exciton spin splitting exceeds the longitudinal optical (LO) phonon energy. Direct experimental evidence has been provided from (1) spin injection from the DMS to an adjacent nonmagnetic quantum well that can be modulated by the LO-assisted spin relaxation and (2) hot exciton photoluminescence within the DMS where a spin flip is accompanied by the emission of one LO phonon.

  • 136.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Kayanuma, K.
    Chen, Z. H.
    Murayama, A.
    Oka, Y.
    Toropov, A. A.
    Sorokin, S. V.
    Ivanov, S. V.
    Kopev, P. S.
    Efficient spin depolarization in ZnCdSe spin detector: an important factor limiting optical spin injection efficiency in ZnMnSe/CdZnSe spin light-emitting structures2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, p. 5260-Article in journal (Refereed)
    Abstract [en]

     Spin depolarization of a ZnCdSe quantum-well spin detector (SD) in ZnMnSe/ZnCdSe light-emitting quantum structures is investigated by cw and time-resolved optical orientation spectroscopy. It is shown that spin depolarization is governed by three distinct spin relaxation processes with the corresponding polarization decay times of 850, 30, and <10 ps. The dominant and the fastest process is attributed to spin relaxation accompanying energy relaxation of hot excitons (and hot carriers) within the SD, providing evidence that it can be an important source of spin loss, leading to the observed limited efficiency of optical spin injection in the structures.

  • 137.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Murayama, A.
    Furuta, T.
    Oka, Y.
    Norton, D. P.
    Pearton, S. J.
    Osinsky, A.
    Dong, J. W.
    Dominant factors limiting efficiency of optical spin detection in ZnO-based materials2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, p. 092103-Article in journal (Refereed)
    Abstract [en]

    Two dominant factors limiting efficiency of optical spin detection in ZnO-based materials system are identified from time-resolved optical orientation and magneto-optical studies. The first is related to the fundamental band structure of the materials characterized by a weak spin-orbit interaction. It leads to cancellation of circular polarization from the optical transitions between the conduction band and the A and B valence band states, which would otherwise carry the desired information on spin polarization of carriers. The second limiting factor is shown to be efficient carrier/exciton spin relaxation, i.e., about 45-80 ps.

  • 138.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Murayama, A.
    Oka, Y.
    Pearton, S. J.
    Norton, D. P.
    Abernathy, C. R.
    Osinsky, A.
    Dong, J. W.
    Spin injection and spin detection in semiconductor quantum structures2008In: First Nordic Workshop on Spintronics and Nanomagnetism,2008, 2008Conference paper (Other academic)
  • 139.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Wang, X. J.
    Tu, C. W.
    University of California, La Jolla, California, United States.
    Ptak, Aaron J.
    National Renewable Energy Lab, Golden, Colorado, United States.
    Geelhaar, L.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    How to Deactivate Harmful Defects and Active them for New Spin Functionalities in a Semiconductor?2015In: Abstract Book, 2015, p. FF3.02-Conference paper (Refereed)
    Abstract [en]

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

  • 140.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Rudko, G. Yu.
    Toropov, A. A.
    Sorokin, S. V.
    Ivanov, S. V.
    Kopev, P. S.
    Malshukov, A. G.
    Chao, K. A.
    Linköping University.
    Effect of magnetic field on exciton spin relaxation in ZnMnSe2002Conference paper (Refereed)
    Abstract [en]

       

  • 141.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Sörman, E.
    Hai, P. N.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    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.
    Magneto-optical spectroscopy of defects in wide bandgap semiconductors: GaN and SiC2000In: Proceedings Conference on Optoelectronic and Microelectronic Materials and Devices, IEEE , 2000, p. 497-502Conference paper (Refereed)
    Abstract [en]

    We review recent progress in our understanding of intrinsic defects in GaN and SiC, gained from magneto-optical studies by Zeeman measurements and optically detected magnetic resonance. The two best-known intrinsic defects in these two wide bandgap semiconductors, i.e. the Ga interstitial in GaN and the silicon vacancy in SiC, are discussed in detail. The Ga interstitial is the first and only intrinsic defect in GaN that has so far been unambiguously identified, either in the presumably isolated form or in a family of up to three complexes. The silicon vacancy is among the most studied intrinsic defect in SiC, at least in two charge states, and yet still remains controversial.

  • 142.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Toropov, A. A.
    Sorokin, S. V.
    Ivanov, S. V.
    Kopev, P. S.
    Optical spin manipulation of ZnMnSe based quantum structures2003In: 204th Annual Meeting of the Electrochemical Society,2003, 2003Conference paper (Other academic)
  • 143.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Tu, C. W.
    Applications of defect engineering in InP-based structures2000Conference paper (Refereed)
    Abstract [en]

     Recent developments in defect engineered InP-based structures, by grown-in intrinsic defects, are reviewed. We demonstrate that n-type doping or modulation doping in InP-based structures can be realized by an intentional introduction of PIn antisites during off-stoichiometric growth of InP at low temperatures (LT) (not, vert, similar260-350°C) by gas source molecular beam epitaxy (GS-MBE), without requiring an external shallow impurity doping source. We shall first summarize our present understanding of the mechanism responsible for the n-type conductivity of LT-InP, which is attributed to the auto-ionization of PIn antisites via the (0/+) level resonant with the conduction band. The PIn antisites are shown to exhibit properties meeting basic requirements for a dopant: (1) known chemical identification; (2) known electronic structure; (3) a control of doping concentration by varying growth temperature. We shall also provide a review of recent results from defect engineering, by utilizing the intrinsic n-type dopants of PIn antisites for modulation doping in InP-based heterostructures. Important issues such as doping efficiency, electron mobility, thermal stability, etc., will be addressed, in a close comparison with the extrinsically doping method by shallow dopants. 

  • 144.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Tu, C. W.
    Defects in dilute nitrides: significance and experimental signatures2004Conference paper (Refereed)
    Abstract [en]

    A brief review of experimental results of defects in dilute nitrides studied by various techniques reported so far in the literature is given. The emphasis is on experimental signatures of grown-in defects in Ga(In)NAs and Ga(Al)NP, which are expected to play important roles in device performance and in determining the success of this novel material system for applications in optoelectronics. The authors' recent results from optically detected magnetic resonance studies of grown-in intrinsic defects, i.e. AsGa antisite in Ga(In)NAs and Ga self-interstitials in Ga(Al,In)NP, are discussed in more detail, in an effort to provide detailed information on the chemical identification and the formation mechanism of the defects as well as to reveal their role in degrading the optical quality of the materials. The review aims not only to provide an overview of the present knowledge and understanding of defects in dilute nitrides, but also to stress the urgent need for concerted efforts to positively identify the most important defects that are harmful to device performance and to design strategies to suppress them during growth or to eliminate them by post-growth treatments.

  • 145.
    Chen, Weimin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Ga(In)NAs Dilute Nitride: An Unconventional Spintronic Semiconductor.2014In: Abstract Book of the 56th Electronic Materials Conference, 2014, p. 51-Conference paper (Refereed)
  • 146.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Tu, C. W.
    Understanding the electronic properties of dilute nitrides relevant to optoelectronic applications2003In: 50th American Vacuum Society Symposium,2003, 2003Conference paper (Other academic)
  • 147.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, CW
    Yonezu, H
    Point defects in dilute nitride III-N-As and III-N-P2006Conference paper (Refereed)
    Abstract [en]

    We provide a brief review of our recent results from optically detected magnetic resonance studies of grown-in non-radiative defects in two most important dilute nitride system s-Ga(In)NAs grown on GaAs substrates and Ga(Al,In)NP grown on Si and GaP substrates. These results have led to the identification of defect complexes in the alloys, involving intrinsic defects such as As-Ga, antisites and Ga-i self-interstitials. They have also shed light on formation mechanisms of the defects and on their role in non-radiative carrier recombination that is harmful to the performance of potential optoelectronic and photonic devices based on these dilute nitrides. (c) 2005 Elsevier B.V. All rights reserved.

  • 148.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wagner, Matthias
    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 .
    Lindström, J. L.
    Amano, H.
    Akasaki, I.
    Role of the Substitutional Oxygen Donor in the Residual n-type Conductivity in GaN1999Conference paper (Refereed)
    Abstract [en]

     A detailed photoluminescence (PL) study reveals a striking similarity in local vibrational properties of a defect center in GaN as compared to that for the substitutional OP donor in GaP. This observation could be interpreted as if the center is in fact related to the substitutional oxygen donor in GaN. The deep-level nature experimentally determined for the defect center calls for caution of a commonly referred model that the substitutional oxygen donor is responsible for the residual n-type conductivity in GaN.

  • 149.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Hai, P. N.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Xin, H. P.
    Tu, C. W.
    Optical Detection of Cyclotron Resonance (ODCR) in GaNAs/GaAs Quantum Well Structures2000Conference paper (Refereed)
    Abstract [en]

    ODCR has been employed to study effective masses and carrier recombination in GaNAs/GaAs multi-quantum well (MQW) structures, prepared by MBE with the nitrogen composition up to 4.5 above GaAs bandgap excitation consists of the excitonic recombination within the GaNAs MQW, the band edge PL emissions from GaAs and a broad 0.8-eV PL of unknown origin. When monitoring these emissions under the above GaAs excitation, the ODCR spectrum is dominated by the electron and hole CR in GaAs, with effective mass values 0.07m0 and 0.5m_0, respectively. The ODCR mechanism is discussed in terms of hot carrier effects, resulting in a reduced carrier recombination in GaAs and an enhanced carrier trapping in the GaNAs MQW. Under resonant excitation of the GaNAs MQW only a broad ODCR signal can be observed corresponding to an effective mass value 0.1m_0, attributed to the electron CR in the GaNAs MQW, where a higher electron effective mass value and a much lower mobility are expected.

  • 150.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Hai, P. N.
    Wagner, Matthias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Amano, H.
    Akasaki, I.
    Xin, H. P.
    Tu, C. W.
    Optical and Microwave Double Resonance of III-nitrides1999In: Joint International Meeting the 196th Meeting of The Electrochemical Society ECS and the 1999 Fall Meeting of The Electrochemical Society of Japan ECSJ,1999, 1999, p. 764-Conference paper (Other academic)
    Abstract [en]

      

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