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  • 1.
    Buyanova, Irina A
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Seppänen, Timo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pearton, SJ
    Polimeni, A
    Capizzi, M
    Brandt, MS
    Bihler, C
    Hong, YG
    Tu, CW
    Unusual effects of hydrogen on electronic and lattice properties of GaNP alloys2006In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 376, p. 568-570Article in journal (Refereed)
    Abstract [en]

    Hydrogen incorporation is shown to cause passivation of various N-related localized states and partial neutralization of N-induced changes in the electronic structure of the GaNxP1-x alloys with x < 0.008. According to the performed X-ray diffraction measurements, the hydrogenation is also found to cause strong expansion of the GaNP lattice which even changes from a tensile strain in the as-grown GaNP epilayers to a compressive strain in the post-hydrogenated structures with the highest H concentration. By comparing results obtained using two types of hydrogen treatments, i.e. by implantation from a Kaufman source and by using a remote dc H plasma, the observed changes are shown to be inherent to H due to its efficient complexing with N atoms, whereas possible effects of implantation damage are only marginal. (c) 2005 Elsevier B.V. All rights reserved.

  • 2.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Izadifard, Morteza
    Physics Department, Shahrood University of Technology, Shahrood, Iran .
    Hong, Y.G.
    Department of Electrical and Computer Engineering, University of California, La Jolla, CA, USA.
    Tu, C.W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, CA, USA.
    Role of nitrogen in photoluminescence up-conversion in GaInNP/GaAs heterostructures2007In: AIP Conference Proceedings / Volume 893 / [ed] Wolfgang Jantsch, Friedrich Schaffler, American Institute of Physics (AIP), 2007, p. 381-382Conference paper (Other academic)
    Abstract [en]

    Alloying of disordered GaInP with nitrogen is shown to lead to very efficient PLU in GaInNP/GaAs heterostructures grown by gas source molecular beam epitaxy (GS‐MBE). This is attributed to the N‐induced changes in the band alignment at the GaInNP/GaAs heterointerface from the type I for the N‐free structure to the type II in the samples with N compositions exceeding 0.5%. Based on the performed excitation power dependent measurements, a possible mechanism for the energy upconversion is suggested as being due to the two‐step two‐photon absorption. The photon recycling effect is shown to be important for the structures with N=1%, from time‐resolved PL measurements. © 2007 American Institute of Physics

  • 3.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Pearton, S.J.
    Bihler, C.
    Brandt, M.S.
    Hong, Y.G.
    Tu, C.W.
    Hydrogen passivation of nitrogen in GaNAs and GaNP alloys: How many H atoms are required for each N atom?2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 2, p. 021920-Article in journal (Refereed)
    Abstract [en]

    Secondary ion mass spectrometry and photoluminescence are employed to evaluate the origin and efficiency of hydrogen passivation of nitrogen in GaNAs and GaNP. The hydrogen profiles are found to closely follow the N distributions, providing unambiguous evidence for their preferential binding as the dominant mechanism for neutralization of N-induced modifications in the electronic structure of the materials. Though the exact number of H atoms involved in passivation may depend on the conditions of the H treatment and the host matrixes, it is generally found that more than three H atoms are required to bind to a N atom to achieve full passivation for both alloys. © 2007 American Institute of Physics.

  • 4.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Wei Min
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Kim, J.
    Ren, F.
    Thaler, G.
    Abernathy, C.R.
    Pearton, S.J.
    Pan, C.-C.
    Chen, G.-T.
    Chyi, J.-I.
    Zavada, J.M.
    Spin injection and spin loss in GaMnN/InGaN Light-Emitting Diodes2005In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 772, p. 1399-1400Article in journal (Refereed)
  • 5.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Kim, J.
    Ren, F.
    Thaler, G.
    Abernathy, C. R.
    Pearton, S. J.
    Pan, C.-C.
    Chen, G.-T.
    Chyi, J. Y.
    Zavada, J. M.
    On the origin of spin loss in GaMnN/InGaN Light-Emitting Diodes2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, p. 2599-Article in journal (Refereed)
    Abstract [en]

     Spin polarization of GaMnN/InGaN light-emitting diodes grown by molecular beam epitaxy is analyzed. In spite of the ferromagnetic behavior of the GaMnN spin injector, the diodes are shown to exhibit very low efficiency of spin injection. Based on resonant optical orientation spectroscopy, the spin loss in the structures is shown to be largely due to fast spin relaxation within the InGaN spin detector, which itself destroys any spin polarization generated by optical spin orientation or electrical spin injection.

  • 6.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Kim, J.
    Ren, F.
    Thaler, G.
    Abernathy, C. R.
    Pearton, S. J.
    Pan, C.-C.
    Chen, G.-T.
    Chyi, J.-I.
    Zavada, J. M.
    On spin injection in GaMnN/InGaN Light-Emitting Diodes2004In: 3rd International Conference on Physics and Applications of Spin-Related Phenomena in Semiconductors PASPS III,2004, 2004Conference paper (Other academic)
  • 7.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Kim, J.
    Ren, F.
    Thaler, G.
    Abernathy, C. R.
    Pearton, S. J.
    Pan, C.-C.
    Chen, G.-T.
    Chyi, J.-I.
    Zavada, J. M.
    Origin of spin loss in GaMnN/InGaN Light-Emitting Diodes2004In: 2nd annual Nano Materials for Defense Applications Symposium,2004, 2004, p. 51-Conference paper (Other academic)
    Abstract [en]

      

  • 8.
    Buyanova, Irina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Izadifard, Morteza
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Polimeni, A.
    Istituto Nazionale di Fisica della Materia, Dipartimento di Fisica, Università degli Studi di Roma “La Sapienza,” Roma, Italy.
    Capizzi, M.
    Istituto Nazionale di Fisica della Materia, Dipartimento di Fisica, Università degli Studi di Roma “La Sapienza,” Roma, Italy.
    Xin, H. P.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California.
    Hydrogen-induced improvements in optical quality of GaNAs alloys2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 21, p. 3662-3665Article in journal (Refereed)
    Abstract [en]

    Strong suppression of potential fluctuations in the band edges of GaNAs alloys due to postgrowth hydrogen treatment, which is accompanied by a reopening of the alloy band gap, is revealed from temperature-dependent photoluminescence (PL) and PL excitation measurements. The effect likely indicates preferential trapping of hydrogen near the lattice sites with the highest nitrogen content. A remarkable improvement in the radiative efficiency of the alloys at room temperature is also demonstrated and is ascribed to efficient hydrogen passivation of competing nonradiative centers.

  • 9.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Xin, H. P.
    Tu, C. W.
    Experimental evidence for N-induced strong coupling of host conduction band states in GaNP: insight into the dominant mechanism for giant band-gap bowing2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, p. 201303-Article in journal (Refereed)
    Abstract [en]

     Direct evidence for N-induced strong coupling of host conduction band (CB) states in GaNxP1-x is provided by photoluminescence excitation. It is manifested as: (1) a drastic change in the ratio of oscillator strengths between the optical transitions involving the CB minimum (CBM) and the high-lying Γ CB state; (2) a strong blueshift of the Γ CB state with increasing x accompanying a redshift of the CBM, (3) pinning of the localized N states and a newly emerging t2 (L or X3) CB state. These findings shed new light on the issue of the dominant mechanism responsible for the giant band-gap bowing of dilute nitrides.

  • 10.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Xin, H. P.
    Tu, C. W.
    Origin of bandgap bowing in GaNP alloys2004Conference paper (Refereed)
    Abstract [en]

     By employing photoluminescence excitation (PLE) spectroscopy, the authors provide direct evidence for N-induced strong coupling and repelling of host conduction band (CB) states in GaNxP1-x. This strong coupling is manifested as (i) a drastic change in the ratio of oscillator strengths between the optical transition near Eg/rGamma and that near the CB minimum (CBM); (ii) a strong blue shift of the a1(Γ) state with increasing N composition accompanying a red shift of the CBM; (iii) pinning of the energies of the N-related levels; and (iv) the appearance of t2(L) or t2(X3) upon N incorporation of which the energy position is insensitive to N compositions. These findings shed new light on the controversial issue of the dominant mechanism responsible for the giant bandgap bowing of dilute nitrides.

  • 11.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Xin, H.P.
    Tu, C.W.
    Pearton, S.J.
    Effects of N incorporation on the electronic structure of GaNP: Origin of the 2.87 eV optical transition2005Conference paper (Refereed)
    Abstract [en]

    Temperature dependent photoluminescence excitation (PLE) spectroscopy is employed to evaluate basic physical properties of the 2.87 eV absorption peak, recently discovered (I. A. Buyanova et al, PRB 69, 201303 (2004)) in the GaNxP1-x alloys. Whereas appearance of this transition is found to be facilitated by incorporation of N and also H atoms, its intensity does not scale with N content. This questions a possible association of this feature with a N-related localized state. Based on the results of temperature dependent measurements, the involved state is concluded to have a non-$\Gamma $ character. Excitation of the known N-related localized states via this state is found to be non-selective, opposed to that between the N-related centers. The observed properties are shown to be hardly consistent with those predicted for the higher lying localized state of the isolated N atom derived from the Γ conduction band minimum (CBM). Alternative explanations for the ``2.87 eV'' state as being due to either a t2 component of the X3c (or L1c CBM or a level arising from a complex of N and H (in some form) are also discussed.

  • 12.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Chen, Wei Min
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Felici, M.
    Polimeni, A.
    Capizzi, M.
    Hong, Y.G.
    Xin, H.P.
    Tu, C.W.
    Unusual effects of hydrogen in GaNP alloys: A general property of dilute nitrides2005In: 2005 MRS Spring Meeting,2005, 2005, p. 135-Conference paper (Other academic)
  • 13.
    Buyanova, Irina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Izadifard, Morteza
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Felici, M.
    Dipartimento di Fisica, Università di Roma “La Sapienza,” Roma, Italy .
    Polimeni, A.
    Dipartimento di Fisica, Università di Roma “La Sapienza,” Roma, Italy .
    Capizzi, M.
    Dipartimento di Fisica, Università di Roma “La Sapienza,” Roma, Italy .
    Hong, Y. G.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California, USA .
    Xin, H. P.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California, USA .
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California, USA .
    Direct experimental evidence for unusual effects of hydrogen on the electronic and vibrational properties of GaNxP1−x alloys: a proof for a general property of dilute nitrides2004In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 70, no 24, p. 245215-245219Article in journal (Refereed)
    Abstract [en]

    Direct experimental evidence for dramatic effects of hydrogen incorporation on the electronic structure and lattice properties of GaNxP1−x alloys is presented. By employing photoluminescence excitation spectroscopy, postgrowth hydrogenation is shown to reopen the band gap of the GaNP alloys and to efficiently reduce the N-induced coupling between the conduction band states. By Raman spectroscopy, these effects are shown to be accompanied by hydrogen-induced breaking of the Ga-P bond in the alloy, evident from disappearance of the corresponding vibrational mode. According to the performed Raman and x-ray diffraction measurements, the hydrogenation is also found to cause a strong expansion of the GaNP lattice, which changes the sign of strain from tensile in the as-grown GaNP epilayers to compressive in the posthydrogenated structures, due to the formation of complexes between N and H.

  • 14.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Polimeni, A.
    Capizzi, M.
    Hong, Y. G.
    Tu, C. W.
    Effects of hydrogen on electronic and crystalline structure of GaNP2004In: EMRS-2004 Spring Meeting,2004, 2004Conference paper (Other academic)
  • 15.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Kasic, A.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Xin, H. P.
    Hong, Y. G.
    Tu, C. W.
    Analysis of band anticrossing in GaNxP1-x alloys2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 70, p. 085209-Article in journal (Refereed)
    Abstract [en]

     Temperature-dependent absorption, photoluminescence excitation, and spectroscopic ellipsometry measurements are employed to accurately determine compositional and temperature dependences of the conduction band (CB) states in GaNP alloys. The CB edge and the higher lying Γc CB minimum (CBM) are shown to exhibit an apparently anticrossing behavior, i.e., the N-induced redshift of the bandgap energy is accompanied by a matching blueshift of the Γc CBM. The obtained data can be phenomenologically described by the band anticrossing model. By considering strong temperature dependence of the energy of the interacting N level, which has largely been overlooked in earlier studies of GaNP, the interacting N level can be attributed to the isolated substitutional NP and the coupling parameter is accurately determined.

  • 16.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Kasic, A.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Xin, H.P.
    Hong, Y.G.
    Tu, C.W.
    Compositional Dependence of conduction band states in GaNP alloys2004In: 5th International Conference on Low Dimensional Structures and Devices,2004, 2004, p. 64-Conference paper (Other academic)
  • 17.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Storasta, Liutauras
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Kim, J.
    Ren, F.
    Thaler, G.
    Abernathy, C. R.
    Pearton, S. J.
    Pan, C.-C.
    Chen, G.-T.
    Chyi, J.-I.
    Zavada, J. M.
    Optical and electrical characterization of (Ga,Mn)N/InGaN multiquantum well light-emitting diodes2004In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 33, no 5, p. 467-471Article in journal (Refereed)
    Abstract [en]

     (Ga,Mn)/N/InGaN multiquantum well (MQW) diodes were grown by molecular beam epitaxy (MBE). The current-voltage characteristics of the diodes show the presence of a parasitic junction between the (Ga,Mn)N and the n-GaN in the top contact layer due to the low conductivity of the former layer. Both the (Ga,Mn)N/InGaN diodes and control samples without Mn doping show no or very low (up to 10% at the lowest temperatures) optical (spin) polarization at zero field or 5 T, respectively. The observed polarization is shown to correspond to the intrinsic optical polarization of the InGaN MQW, due to population distribution between spin sublevels at low temperature, as separately studied by resonant optical excitation with a photon energy lower than the bandgap of both the GaN and (Ga,Mn)N. This indicates efficient losses in the studied structures of any spin polarization generated by optical spin orientation or electrical spin injection. The observed vanishing spin injection efficiency of the spin light-emitting diode (LED) is tentatively attributed to spin losses during the energy relaxation process to the ground state of the excitons giving rise to the light emission.

  • 18.
    Izadifard, Morteza
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Optical characterization of dilute nitride semiconductors and related quantum structures2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Dilute nitrides (i.e. nitrogen-containing, anion-mixed III-V ternary and quaternary alloys) have recently attracted much attention due to their unusual fundamental properties promising for device applications in optoelectronics and photonics, such as highly efficient and low cost near infrared lasers, efficient visible light emitting diodes (LEDs), multi-junction solar cells, as well as heterojunction bipolar transistors (HBTs). In order to fully explore the potential of these new materials, detailed knowledge on their fundamental and material-related properties is required.

    The work presented in this thesis focuses on optical studies of the electronic structure, radiative recombination processes and also characterization of material properties of several dilute nitrides systems that are relevant to device applications, such as GaNP/GaP, GaNP/Si, GaNAs/GaAs and GaInNP/GaAs. The thesis is divided into two parts. The first part includes five chapters that give a general introduction to the research field and also describes experimental methods utilized in the research work. The second part contains seven original scientific papers.

    Papers I and II report detailed studies of effects of post-growth hydrogen incorporation on the electronic structure of GaNAs and GaNP alloys by using photoluminescence (PL), PL excitation (PLE), and Raman spectroscopies, as well as high resolution X-ray diffraction (HRXRD) measurements. Introduction of hydrogen in the alloys was found to cause passivation of N-related localized states. Additionally, profound and rather astonishing changes in the band structure upon H incorporation were observed, such as a recovery of the bandgap energies of the parental GaAs and GaP, i.e. deactivation of the N-induced bandgap bowing. In GaNP, this was accompanied by a reduction in the N-induced coupling between the conduction band states. Raman spectroscopy has showed that these effects are related to hydrogeninduced breaking of the Ga-N bond. Raman and HRXRD measurements have also shown that the hydrogenation caused a strong expansion of the GaNP lattice, which changes the sign of strain from tensile strain in the as-grown GaNP epilayers to compressive strain after hydrogenation, due to formation of complexes between N and H.

    Paper III-IV discuss optical quality and defect properties of GaNP/Si and GaNP /GaP alloys, as well as effects of rapid thermal annealing (RTA). By employing a variety of optical characterization techniques including cathodoluminescence (CL), cw- and time-resolved PL, PLE, and optically detected magnetic resonance (ODMR), high optical quality of the GaN0.018P0.982 epilayers lattice matched to Si substrates was demonstrated and was shown to be comparable to that of the “state-of-the-art" GaNP alloys grown on GaP substrates. The growth of GaNP on Si is, however, found to facilitate the formation of several point defects, including complexes involving Ga interstitials (Gai). A reduction and removal of competing non-radiative point defects by RTA has been concluded to be responsible for a substantial increase in radiative efficiency of the GaNP epilayers subjected to the post-growth annealing, evident from reduced thermal quenching of the PL intensity as well as from a substantial increase in carrier lifetime at room temperature.

    Papers V-VII are devoted to detailed studies of Ga0.46In0.54NxP1-x alloys lattice matched to GaAs, by using cw- and time-resolved PL, PLE, and optically detected cyclotron resonance (ODCR) measurements. The type-II band alignment at the Ga0.46In0.54NxP1-x/GaAs interface was concluded with x ≥ 0.5% based on (i) highly efficient photoluminescence upconversion (PLU) observed in the N containing alloys and (ii) appearance of a near-infrared PL emission attributed to the spatially indirect type-II transitions. Compositional dependence of the conduction band offset at the GayIn1-yNxP1-x/GaAs interface was also estimated. Origin of the PLU process was determined as being due to two-step two-photon absorption (TS-TPA). Different from other direct band gap dilute nitrides, the low temperature PL emission was shown to largely arise from radiative transitions involving spatially separated localized electronhole pairs. The observed charge separation was tentatively attributed to the long range CuPt ordering promoted by the presence of nitrogen.

    List of papers
    1. Hydrogen-induced improvements in optical quality of GaNAs alloys
    Open this publication in new window or tab >>Hydrogen-induced improvements in optical quality of GaNAs alloys
    Show others...
    2003 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 21, p. 3662-3665Article in journal (Refereed) Published
    Abstract [en]

    Strong suppression of potential fluctuations in the band edges of GaNAs alloys due to postgrowth hydrogen treatment, which is accompanied by a reopening of the alloy band gap, is revealed from temperature-dependent photoluminescence (PL) and PL excitation measurements. The effect likely indicates preferential trapping of hydrogen near the lattice sites with the highest nitrogen content. A remarkable improvement in the radiative efficiency of the alloys at room temperature is also demonstrated and is ascribed to efficient hydrogen passivation of competing nonradiative centers.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-45047 (URN)10.1063/1.1578513 (DOI)79491 (Local ID)79491 (Archive number)79491 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
    2. Direct experimental evidence for unusual effects of hydrogen on the electronic and vibrational properties of GaNxP1−x alloys: a proof for a general property of dilute nitrides
    Open this publication in new window or tab >>Direct experimental evidence for unusual effects of hydrogen on the electronic and vibrational properties of GaNxP1−x alloys: a proof for a general property of dilute nitrides
    Show others...
    2004 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 70, no 24, p. 245215-245219Article in journal (Refereed) Published
    Abstract [en]

    Direct experimental evidence for dramatic effects of hydrogen incorporation on the electronic structure and lattice properties of GaNxP1−x alloys is presented. By employing photoluminescence excitation spectroscopy, postgrowth hydrogenation is shown to reopen the band gap of the GaNP alloys and to efficiently reduce the N-induced coupling between the conduction band states. By Raman spectroscopy, these effects are shown to be accompanied by hydrogen-induced breaking of the Ga-P bond in the alloy, evident from disappearance of the corresponding vibrational mode. According to the performed Raman and x-ray diffraction measurements, the hydrogenation is also found to cause a strong expansion of the GaNP lattice, which changes the sign of strain from tensile in the as-grown GaNP epilayers to compressive in the posthydrogenated structures, due to the formation of complexes between N and H.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-45014 (URN)10.1103/PhysRevB.70.245215 (DOI)79416 (Local ID)79416 (Archive number)79416 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
    3. Evaluation of optical quality and defect properties of GaNxP1−x alloys lattice matched to Si
    Open this publication in new window or tab >>Evaluation of optical quality and defect properties of GaNxP1−x alloys lattice matched to Si
    Show others...
    2004 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, p. 6347-Article in journal (Refereed) Published
    Abstract [en]

    By using a variety of optical characterization techniques, including cathodoluminescence, temperature-dependent cw- and time-resolved photoluminescence (PL), and PL excitation spectroscopies, high optical quality of the GaN0.018P0.982 epilayers lattice matched to Si substrates is demonstrated and is shown to be comparable to that of the “state-of-the-art” GaNP alloys grown on GaP substrates. The growth of GaNP on Si is, however, found to facilitate the formation of several point defects, including complexes involving Ga interstitial atoms (Gai).

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-45010 (URN)10.1063/1.1839286 (DOI)79412 (Local ID)79412 (Archive number)79412 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
    4. Effects of rapid thermal annealing on optical properties of GaNxP1−x alloys grown by solid source molecular beam epitaxy
    Open this publication in new window or tab >>Effects of rapid thermal annealing on optical properties of GaNxP1−x alloys grown by solid source molecular beam epitaxy
    Show others...
    2005 (English)In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 20, no 5, p. 353-356Article in journal (Refereed) Published
    Abstract [en]

    Temperature-dependent photoluminescence (PL), PL excitation and time-resolved PL measurements were employed to study the effects of rapid thermal annealing (RTA) on optical properties of GaNxP1−x alloys grown by solid source molecular beam epitaxy. A substantial increase in radiative efficiency of GaNP epilayers, which is especially pronounced for the high-energy PL component, was achieved after RTA and is attributed to annealing out of competing non-radiative centres. The latter is evident from reduced quenching of the PL intensity with increasing measurement temperature, which results in a strong increase (up to 18 times) in the PL intensity at room temperature (RT), as well as from a substantial increase in carrier lifetime at RT deduced from time-resolved PL measurements.

    National Category
    Natural Sciences Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-30725 (URN)10.1088/0268-1242/20/5/005 (DOI)16338 (Local ID)16338 (Archive number)16338 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
    5. Band alignment in GaInNP/GaAs heterostructures grown by gas-source molecular-beam epitaxy
    Open this publication in new window or tab >>Band alignment in GaInNP/GaAs heterostructures grown by gas-source molecular-beam epitaxy
    Show others...
    2005 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, no 26, p. 261904-Article in journal (Refereed) Published
    Abstract [en]

    Low-temperature photoluminescence (PL), PL excitation, and optically detected cyclotron resonance measurements are employed to determine band alignment in GaInNP/GaAs heterostructures grown by gas-source molecular-beam epitaxy. The type II band alignment at the Ga0.46In0.54NxP1−x/GaAs interface is concluded for the alloys with x ≥ 0.5% based on (i) highly efficient PL upconversion observed in the N containing samples and (ii) appearance of a near-infrared PL emission attributed to the spatially indirect type II transitions. Compositional dependence of the conduction band offset at the Ga1−yInyNxP1−x/GaAs interface is also estimated.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-50479 (URN)10.1063/1.1952586 (DOI)
    Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
    6. Photoluminescence upconversion in GaInNP/GaAs heterostructures grown by gas source molecular beam epitaxy
    Open this publication in new window or tab >>Photoluminescence upconversion in GaInNP/GaAs heterostructures grown by gas source molecular beam epitaxy
    Show others...
    2006 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, no 7, p. 073515-Article in journal (Refereed) Published
    Abstract [en]

    Properties of photoluminescence (PL) upconversion (PLU) in GaInNP/GaAs heterostructures are studied in detail by employing a number of optical spectroscopies. Based on excitation power dependent and temperature dependent PL measurements, the upconverted PL from GaInNP under optical excitation below its band gap is attributed to radiative transitions involving spatially separated localized electron-hole pairs, which is of a similar origin as the near-band-gap emission detected under optical excitation above the GaInNP band gap. The PLU process is shown to be largely promoted by increasing N content in the GaInNP alloys, due to a N-induced change in the band alignment at the GaInNP/GaAs heterointerface from the type I in the N-free structure to the type II in the samples with N compositions exceeding 0.5%. A possible mechanism for the energy upconversion is discussed in terms of two-step two-photon absorption. The photon recycling effect is shown to be important for the structures with N = 1%.

    National Category
    Engineering and Technology Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-50252 (URN)10.1063/1.2188087 (DOI)
    Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
    7. Radiative recombination of GaInNP alloys lattice matched to GaAs
    Open this publication in new window or tab >>Radiative recombination of GaInNP alloys lattice matched to GaAs
    Show others...
    2006 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 1, p. 011919-Article in journal (Refereed) Published
    Abstract [en]

    Cw- and time-resolved photoluminescence (PL) spectroscopy is employed to evaluate dominant mechanisms for light emission in GayIn1−yNxP1−x alloys grown by gas source molecular-beam epitaxy on GaAs substrates. Different from other direct band gap dilute nitrides, the low temperature PL emission was shown to be largely attributed to radiative transitions involving spatially separated localized electron-hole pairs. The observed charge separation is tentatively attributed to the long range CuPt ordering promoted by the presence of nitrogen.

    National Category
    Natural Sciences Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-36494 (URN)10.1063/1.2161118 (DOI)31451 (Local ID)31451 (Archive number)31451 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
  • 19.
    Izadifard, Morteza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Buyanova, Irina A.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hong, Y.G.
    Department of Electrical and Computer Engineering, University of California, San Diego, CA.
    Tu, C.W.
    Department of Electrical and Computer Engineering, University of California, San Diego, CA.
    Photoluminescence upconversion in GaInNP/GaAs heterostructures grown by gas source molecular beam epitaxy2006In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, no 7, p. 073515-Article in journal (Refereed)
    Abstract [en]

    Properties of photoluminescence (PL) upconversion (PLU) in GaInNP/GaAs heterostructures are studied in detail by employing a number of optical spectroscopies. Based on excitation power dependent and temperature dependent PL measurements, the upconverted PL from GaInNP under optical excitation below its band gap is attributed to radiative transitions involving spatially separated localized electron-hole pairs, which is of a similar origin as the near-band-gap emission detected under optical excitation above the GaInNP band gap. The PLU process is shown to be largely promoted by increasing N content in the GaInNP alloys, due to a N-induced change in the band alignment at the GaInNP/GaAs heterointerface from the type I in the N-free structure to the type II in the samples with N compositions exceeding 0.5%. A possible mechanism for the energy upconversion is discussed in terms of two-step two-photon absorption. The photon recycling effect is shown to be important for the structures with N = 1%.

  • 20.
    Izadifard, Morteza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hong, Y.G.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California.
    Tu, C.W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California.
    Radiative recombination of GaInNP alloys lattice matched to GaAs2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 1, p. 011919-Article in journal (Refereed)
    Abstract [en]

    Cw- and time-resolved photoluminescence (PL) spectroscopy is employed to evaluate dominant mechanisms for light emission in GayIn1−yNxP1−x alloys grown by gas source molecular-beam epitaxy on GaAs substrates. Different from other direct band gap dilute nitrides, the low temperature PL emission was shown to be largely attributed to radiative transitions involving spatially separated localized electron-hole pairs. The observed charge separation is tentatively attributed to the long range CuPt ordering promoted by the presence of nitrogen.

  • 21.
    Izadifard, Morteza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vorona, Igor
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Utsumi, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan .
    Furukawa, Y.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan .
    Moon, S.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan .
    Wakahara, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan .
    Yonezu, H.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan .
    Evaluation of optical quality and defect properties of GaNxP1−x alloys lattice matched to Si2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, p. 6347-Article in journal (Refereed)
    Abstract [en]

    By using a variety of optical characterization techniques, including cathodoluminescence, temperature-dependent cw- and time-resolved photoluminescence (PL), and PL excitation spectroscopies, high optical quality of the GaN0.018P0.982 epilayers lattice matched to Si substrates is demonstrated and is shown to be comparable to that of the “state-of-the-art” GaNP alloys grown on GaP substrates. The growth of GaNP on Si is, however, found to facilitate the formation of several point defects, including complexes involving Ga interstitial atoms (Gai).

  • 22.
    Izadifard, Morteza
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Vorona, Igor
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Utsumi, A.
    Furukawa, Y.
    Moon, S.
    Wakahara, A.
    Yonezu, H.
    GaNxP1-x Alloys Lattice Matched to Si: A Novel Material System for Nano- Applications2005In: 3rd annual Nano Materials for Defense Applications Symposium,2005, 2005, p. 26-Conference paper (Other academic)
  • 23.
    Izadifard, Morteza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Utsumi, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan.
    Furukawa, Y.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan.
    Wakahara, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan.
    Yonezu, H.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, Japan.
    Effects of rapid thermal annealing on optical properties of GaNxP1−x alloys grown by solid source molecular beam epitaxy2005In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 20, no 5, p. 353-356Article in journal (Refereed)
    Abstract [en]

    Temperature-dependent photoluminescence (PL), PL excitation and time-resolved PL measurements were employed to study the effects of rapid thermal annealing (RTA) on optical properties of GaNxP1−x alloys grown by solid source molecular beam epitaxy. A substantial increase in radiative efficiency of GaNP epilayers, which is especially pronounced for the high-energy PL component, was achieved after RTA and is attributed to annealing out of competing non-radiative centres. The latter is evident from reduced quenching of the PL intensity with increasing measurement temperature, which results in a strong increase (up to 18 times) in the PL intensity at room temperature (RT), as well as from a substantial increase in carrier lifetime at RT deduced from time-resolved PL measurements.

  • 24.
    Izadifard, Morteza
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Utsumi, A.
    Furukawa, Y.
    Wakahara, A.
    Yonezu, H.
    Effects of rapid thermal annealing on optical quality of GaNP alloys2004In: EMRS-2004 Spring Meeting,2004, 2004, Vol. 151, p. 335-Conference paper (Refereed)
    Abstract [en]

    Significant improvements in radiative efficiency of GaNP epilayers grown on GaP substrates by solid-source molecular beam epitaxy (MBE) are achieved by post-growth rapid thermal annealing (RTA). From temperature-dependent CW and time-resolved photoluminescence (PL) spectroscopies combined with PL excitation measurements, the observed improvements are attributed to annealing out of competing nonradiative centres. This conclusion is supported by the following experimental evidence: reduced thermal quenching of the PL intensity resulting in a substantial (up to 18 times) increase at room temperature (RT) after RTA, and simultaneous improvements in carrier lifetime at RT deduced from time-resolved PL measurements.

  • 25.
    Izadifard, Morteza
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Polimeni, A.
    Capizzi, M.
    Tu, C. W.
    Role of hydrogen in improving optical quality of GaNAs alloys2003In: 11th Int. Conf. on Narrow Bandgap Semiconductors,2003, Physica E, Vol 20: Elsevier , 2003, p. 313-316Conference paper (Refereed)
    Abstract [en]

    Effects of hydrogen irradiation on optical quality of GaNxAs1−x alloys grown by gas source molecular beam epitaxy are studied by photoluminescence (PL) and PL excitation spectroscopies. A strong blue shift of the alloy band gap towards the value of a reference N-free GaAs samples is revealed. Substantial improvements in the optical quality of the structures induced by hydrogen, due to a reduction of band edge potential fluctuations, is also demonstrated. The effect is tentatively attributed to the preferential trapping of hydrogen atoms at the lattice sites with the highest N compositions, which leads to the neutralization of electronic states contributing to the band tail states as well as to the improvement in strain uniformity.

  • 26.
    Izadifard, Morteza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Mtchedlidze, T.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Vorona, Igor
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Buyanova, Irina A.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hong, Y.G.
    Department of Electrical and Computer Engineering, University of California, San Diego, CA.
    Tu, C.W.
    Department of Electrical and Computer Engineering, University of California, San Diego, CA.
    Band alignment in GaInNP/GaAs heterostructures grown by gas-source molecular-beam epitaxy2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, no 26, p. 261904-Article in journal (Refereed)
    Abstract [en]

    Low-temperature photoluminescence (PL), PL excitation, and optically detected cyclotron resonance measurements are employed to determine band alignment in GaInNP/GaAs heterostructures grown by gas-source molecular-beam epitaxy. The type II band alignment at the Ga0.46In0.54NxP1−x/GaAs interface is concluded for the alloys with x ≥ 0.5% based on (i) highly efficient PL upconversion observed in the N containing samples and (ii) appearance of a near-infrared PL emission attributed to the spatially indirect type II transitions. Compositional dependence of the conduction band offset at the Ga1−yInyNxP1−x/GaAs interface is also estimated.

  • 27.
    Syväjärvi, Mikael
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Nasi, L.
    Yazdi, Gholamreza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Salviati, G.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Formation of ferromagnetic SiC: Mn phases2005In: Materials Science Forum, Vols. 483-485, 2005, Vol. 483-485, p. 241-244Conference paper (Refereed)
    Abstract [en]

    Ferromagnetic phases in as-grown SiC have been studied. An interpretation about the formation based on details of the phase appearance in the layers from optical microscopy, AFM, and TEM investigations is related to the growth. Some phases were found to have a nucleation at the edge of the phase and detailed TEM investigations show that the phases have an increased grain density at the edge while the main part of the phase is monocrystalline.

  • 28.
    Syväjärvi, Mikael
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Stanciu, V.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Chen, Weimin
    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.
    Svedlindh, P.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    As-grown 4H-SiC epilayers with magnetic properties2004In: SILICON CARBIDE AND RELATED MATERIALS 2003, PRTS 1 AND 2, 2004, p. 747-750Conference paper (Refereed)
    Abstract [en]

    A growth process for diluted magnetic SiC has been explored for as-grown epitaxiallayers by introducing Mn ions. Depending on the growth conditions, either high Mn doping orexcess concentrations with second phases may form in the layers. Under those conditions wherecompound phases appear, there is a magnetic response in the material as demonstrated usingSQUID measurements with a transition temperature of 160K in the as-grown material. There is noresponse in layers for which the second phases have been removed by etching.

  • 29. Thinh, N. Q.
    et al.
    Vorona, Igor
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Hong, Y. G.
    Xin, H. P.
    Tu, C. W.
    Formation of Ga interstitials in (Al,In)yGa1-yNxP1-x alloys and their role in carrier recombination2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, p. 2827-Article in journal (Refereed)
    Abstract [en]

    Formation of complex defects involving a Ga interstitial (Gai) in (Al,In)yGa1-yNxP1-x alloys and their effects on optical quality are studied by photoluminescence (PL) and optically detected magnetic resonance spectroscopies. Introduction of these defects is shown to be largely promoted by incorporation of N. In quaternary alloys, concentrations of the defects are found to critically depend on the group III atoms that replace Ga, i.e., it is largely enhanced by the presence of Al in alloys, but is only marginally affected by In incorporation. The effect is attributed to differences in surface adatom mobilities of the group III atoms involved and their bonding strength with N. The revealed Gai complexes are shown to act as efficient nonradiative recombination centers degrading the PL efficiency. The defects exhibit high thermal stability and can only be partially removed by postgrowth rapid thermal annealing.

  • 30.
    Vorona, Igor
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Mchedlidze, T
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Hong, YG
    Tu, CW
    Signatures of grown-in defects in GaInNP alloys grown on a GaAs substrate from magnetic resonance studies2006In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 376, p. 571-574Article in journal (Refereed)
    Abstract [en]

    Three grown-in defects acting as centers of non-radiative recombination (NR) were detected in GaInNP alloys grown on a GaAs substrate using the optically detected magnetic resonance (ODMR) technique. Among them, one was proposed to be either a Ga-i-related defect or an AS(Ga)-related defect, from the resolved four-line hyperfine structure. The former model was concluded to be more favorable by weighing physical properties of the two defects, e.g. the likelihood for their presence in the studied structures, their spatial location, g-value and effect of rapid thermal annealing (RTA). RTA at 700 degrees C was shown to reduce concentrations of the studied defects but it introduced a new defect that likely directly participates in the monitored radiative recombination process in the RTA-treated samples. (c) 2005 Elsevier B.V. All rights reserved.

  • 31.
    Vorona, Igor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Mtchedlidze, T.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Hong, Y.G.
    Xin, H.P.
    Tu, C.W.
    Magnetic resonance signatures of grown-in defects in GaInNP alloys grown on a GaAs substrate2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, no 22, p. 222110-Article in journal (Refereed)
    Abstract [en]

    Dilute-nitride Ga0.44In0.56NyP1-y alloys with y=0-0.02, grown on a GaAs substrate using gas-source molecular beam epitaxy, are studied by the optically detected magnetic resonance (ODMR) technique. Grown-in paramagnetic defects were found to act as centers of nonradiative recombination. Resolved hyperfine structure for one of the detected ODMR signals suggests involvement of a Ga-interstitial or an As-antisite in the structure of the related defect. © 2005 American Institute of Physics.

1 - 31 of 31
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