| 1. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Mechanism for rapid thermal annealing improvements in undoped GaNxAs1-x/GaAs structures grown by molecular beam epitaxy
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 77:15, s. 2325-
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Tidskriftsartikel (refereegranskat)abstract
- A systematic investigation of the effect of rapid thermal annealing (RTA) on optical properties of undoped GaNAs/GaAs structures is reported. Two effects are suggested to account for the observed dramatic improvement in the quality of the GaNxAs1-x/GaAs quantum structures after RTA: (i) improved composition uniformity of the GaNxAs1-x alloy, deduced from the photoluminescence (PL), PL excitation and time-resolved measurements; and (ii) significant reduction in the concentration of competing nonradiative defects, revealed by the optically detected magnetic resonance studies.
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| 2. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Optical and electronic properties of GaNAs/GaAs structures
- 2000
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Konferensbidrag (refereegranskat)abstract
- We review our recent results from studies of electronic properties of GaNAs/GaAs structures with low nitrogen content, by photoluminescence (PL), PL excitation, time-resolved PL spectroscopies as well as optically detected magnetic resonance (ODMR) and cyclotron resonance (ODCR) studies. The issues to be addressed include key material-related properties and fundamental electronic parameters of the GaNAs alloy, relevant to device applications, such as identification of the dominant recombination processes in the alloy, compositional dependence of the electron effective mass and band alignment in the GaNAs/GaAs heterostructures.
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| 3. |
- Chen, Weimin, 1959-, et al.
(författare)
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Nature and Formation of Non-Radiative Defects in GaNAs and InGaAsN
- 2002
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Ingår i: MRS Fall Meeting 2001,2001. - Materials Research Society Symposium - Proceedings, Vol. 692 : MRS. ; , s. 67-72
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Konferensbidrag (refereegranskat)abstract
- The optically detected magnetic resonance (ODMR) technique has been employed to examine the nature and formation mechanism of non-radiative defects in GaNAs and InGaAsN. In both alloys, two defects were observed and were shown to be deep-level, non-radiative recombination centers. One of the defects has been identified as a complex involving an AsGa antisite. These two defects gain more importance with increasing N composition up to 3%, presumably due to an increase in their concentration. With a further higher N composition, the defects start to lose importance in carrier recombination that is attributed to an increasingly important role of other new non-radiative channels introduced with a high N composition. On the other hand, effect of In composition up to 3% seems to be only marginal. Both defects were shown to be preferably introduced in the alloys during low-temperature growth by molecular beam epitaxy (MBE), but can be rather efficiently removed by post-growth rapid thermal annealing.
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| 4. |
- Chen, Weimin, et al.
(författare)
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P-N defect in GaNP studied by optically detected magnetic resonance
- 2003
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Ingår i: Proceedings of the 22nd International Conference on Defects in Semiconductors. - : Elsevier BV. ; , s. 399-402
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Konferensbidrag (refereegranskat)abstract
- We provide experimental evidence for an intrinsic defect in GaNP from optically detected magnetic resonance (ODMR). This defect is identified as a P-N complex, exhibiting hyperfine structure due to interactions with a nuclear spin I=12 of one P atom and also a nuclear spin I=1 due to one N atom. The introduction of the defect is assisted by the incorporation of N within the studied N composition range of up to 3.1%, under non-equilibrium growth conditions during gas-source molecular beam epitaxy. The corresponding ODMR spectrum was found to be isotropic, suggesting an A1 symmetry of the defect state. The localization of the electron wave function at the P-N defect in GaNP is found to be even stronger than that for the isolated PGa antisite in its parent binary compound GaP. © 2003 Elsevier B.V. All rights reserved.
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| 5. |
- 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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| 6. |
- Thinh, N. Q., et al.
(författare)
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Formation of nonradiative defects in molecular beam epitaxial GaNxAs1-x studied by optically detected magnetic resonance
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 79:19, s. 3089-
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Tidskriftsartikel (refereegranskat)abstract
- The formation of two nonradiative defects (i.e., an AsGa-related complex and an unknown deep-level defect with g = 2.03) in GaNxAs1-x epilayers and GaAs/GaNxAs1-x multiple-quantum-well structures, grown by molecular beam epitaxy, is studied by the optically detected magnetic resonance technique. It is shown that contributions by these defects in competing carrier recombination strongly vary with the nitrogen composition. An increase in the growth temperature or postgrowth rapid thermal annealing significantly reduces the influence of the nonradiative defects studied, and is accompanied by a remarkable improvement in the optical properties of the structures.
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| 7. |
- Thinh, N.Q., et al.
(författare)
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Ga-interstitial related defects in Ga(Al)NP
- 2005
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Ingår i: 27th Int. Conf. on the Physics of Semicond,2004. - : American Institute of Physics (AIP). ; , s. 259-260
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Twogrown-in Ga interstitial (Gai) defects in Ga(Al)NP are identified byoptically detected magnetic resonance (ODMR), from the characteristic hyperfine (HF)structure associated with the nuclear spin I=3/2 of the Gai.Both defects are concluded to be Gai-related complexes. Effects ofAl and N compositions on the HF structure shed lighton local surrounding of the Gai. ©2005 American Institute ofPhysics
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| 8. |
- Thinh, N. Q., et al.
(författare)
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Grown-in intrinsic defect in GaNAs
- 2001
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Ingår i: Proceedings of the 21st International Conference on Defects in Semiconductors.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 9. |
- 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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| 10. |
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| 11. |
- Thinh, N. Q., et al.
(författare)
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Properties of a grown-in intrinsic defect in GaNAs
- 2001
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Ingår i: APS 2001 March Meeting,2001. - Bull. Amer. Phys. Soc. : APS. ; , s. 1185-
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Konferensbidrag (refereegranskat)abstract
- Properties of a grown-in intrinsic defect in GaNAs alloys and GaNAs/GaAs quantum well structures with low N composition have been investigated by optically detected magnetic resonance (ODMR). The characteristic hyperfine (HF) structure, arising from S=1/2 and I=3/2, suggests a complex involving the As_Ga antisite as being the most likely candidate for the responsible defect. The strong HF interaction evidences a high localization of the wavefunction of the unpaired electron near the As_Ga antisite, which is found to be rather insensitive to either N composition or quantum confinement. The formation mechanism for the defect has been studied by varying growth temperature or by performing post-growth rapid thermal annealing. It is shown that the defect can be preferably introduced during molecular beam epitaxy (MBE) growth at low temperature under non-equilibrium conditions, similar to the case of its parental compound GaAs grown under similar conditions.
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| 12. |
- Thinh, N.Q., et al.
(författare)
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Properties of Ga-interstitial defects in AlxGa 1-xNyP1-y
- 2005
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 71:12
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Tidskriftsartikel (refereegranskat)abstract
- A detailed account of the experimental results from optically detected magnetic resonance (ODMR) studies of grown-in defects in (Al)GaNP alloys, prepared by molecular beam epitaxy, is presented. The experimental procedure and an in-depth analysis by a spin Hamiltonian lead to the identification of two Gai defects (Gai-A and Gai-B). New information on the electronic properties of these defects and the recombination processes leading to the observation of the ODMR signals will be provided. These defects are deep-level defects. In conditions when the defect is directly involved in radiative recombination of the near-infrared photoluminescence band, the energy level of the Gai-B defect was estimated to be deeper than ~1.2 eV from either the conduction or valence band edge. In most cases, however, these defects act as nonradiative recombination centers, reducing the efficiency of light emission from the alloys. They can thus undermine the performance of potential photonic devices. High thermal stability is observed for these defects. ©2005 The American Physical Society.
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| 13. |
- Thinh, N. Q., et al.
(författare)
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Signature of an intrinsic point defect in GaNxAs1-x
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 63:3, s. 332031-332034
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Tidskriftsartikel (refereegranskat)abstract
- The first experimental signature of an intrinsic defect in GaNAs is provided from an optically detected magnetic resonance study. The resolved central hyperfine structure identifies the defect with a nuclear spin I = 3/2, containing either an AsGa antisite or a Ga interstitial. From the strength of the hyperfine interaction and the growth conditions, a complex involving the AsGa antisite seems to be a more likely candidate.
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| 14. |
- 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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| 15. |
- Wagner, Matthias, 1969-, et al.
(författare)
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Magneto-optical studies of the 0.88-eV photoluminescence emission in electron-irradiated GaN
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 62:24, s. 16572-16577
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Tidskriftsartikel (refereegranskat)abstract
- Properties of the 0.88-eV photoluminescence (PL) in electron-irradiated wurtzite GaN have been investigated in detail by a combination of various magneto-optical techniques, including Zeeman measurements of PL, optically detected magnetic resonance (ODMR), and level anticrossing (LAC). ODMR observed by monitoring the PL emission is demonstrated to originate from a spin triplet. The symmetry of the corresponding defect is shown to be rhombic with its principal axes pointing into the high-symmetry directions Z=[0001], Y=[11¯00], and X=[112¯0]. From the Zeeman measurements the emission is shown to arise from an optical transition between a singlet excited state and the singlet ground state, providing convincing evidence for indirect detection of the spin triplet ODMR. LAC investigations of the same PL emission reveal two LAC lines, among which one is related to the spin triplet detected in ODMR.
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