| 1. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Analysis of band anticrossing in GaNxP1-x alloys
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70, s. 085209-
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
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| 3. |
- Buyanova, Irina, 1960-, et al.
(författare)
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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
- 2004
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 70:24, s. 245215-245219
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Thinh, N. Q., et al.
(författare)
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Formation of Ga interstitials in (Al,In)yGa1-yNxP1-x alloys and their role in carrier recombination
- 2004
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 85, s. 2827-
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Thinh, N. Q., et al.
(författare)
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Identification of Ga-interstitial defects in GaNyP1−y and AlxGa1−xNyP1−y
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : APS. - 1098-0121 .- 1550-235X. ; 70:12, s. 121201-
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Tidskriftsartikel (refereegranskat)abstract
- Two Ga -interstitial (Gai) defects are identified by optically detected magnetic resonance as common grown-in defects in molecular beam epitaxial GaNyP1−y and AlxGa1−xNyP1−y. Characteristic hyperfine structure arising from spin interaction between an unpaired electron and a Ga nucleus is clearly resolved. The observed strong and nearly isotropic hyperfine interaction reveals an electron wave function of A1 symmetry that is highly localized at the Gai and thus a deep-level defect. Our analysis based on first-principles calculations suggests that these defects are complexes containing one Gai2+ .
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| 9. |
- Vorona, Igor, et al.
(författare)
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Identification of Ga interstitials in GaAlNP
- 2003
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Ingår i: Proceedings of the 22nd International Conference on Defects in Semiconductors. - : Elsevier BV. ; , s. 466-469
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Konferensbidrag (refereegranskat)abstract
- New dilute nitride Ga1-xAlxNyP1-y alloys grown by gas-source molecular beam epitaxy have been studied by the optical detected magnetic resonance technique. Two paramagnetic defect centers with an effective electron spin S = 1/2 were observed and shown to involve Ga interstitials (denoted as Gai-A and Gai-B), both exhibiting the characteristic hyperfine (HF) structure from the two Ga isotopes. The HF interaction is shown to be nearly isotropic and rather strong, providing evidence for an A1 symmetry of the electron wave function highly localized at the Ga atom. We tentatively attribute Gai-A and Gai-B to the interstitial sites surrounded by group-III and group-(V and III) atoms, respectively. © 2003 Elsevier B.V. All rights reserved.
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| 10. |
- Yinru, Chen, et al.
(författare)
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Session comparison measurement and learning in masquerading detection
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In applying command sequence matching to detect masquerading attack, the first important step is to build a user's profile for characterizing normal behavior. In this paper, we proposed a new approach which applies the comparison of arbitrary length of sessions to distinguish users. In this approach, a session is regarded as an integral comparison unit. This method makes it possible to locate command matches in historical command data for long sequences. The testing results show that the method can be used in creating a user's profile. Further, it will pave the road for future work in applying data mining technology to detect potential masqueraders.
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