| 1. |
- Gogova, Daniela, et al.
(författare)
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Fast growth of high quality GaN
- 2003
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Ingår i: Physica status solidi. A, Applied research. - : Wiley. - 0031-8965 .- 1521-396X. ; 200:1, s. 13-17
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Tidskriftsartikel (refereegranskat)abstract
- We have grown bulk-like GaN with a thickness up to 335 μm on 2″ sapphire substrates in a vertical HVPE reactor with a bottom-fed design. A very high growth rate of 250 μm/h is reached with high crystalline quality of the grown material. The low temperature PL spectra show the free A-exciton line at 3.483 eV and rather narrow I2 lines with FWHM of 1–2 meV indicating high crystalline quality and low doping concentration. This HVPE-GaN has the potential to provide lattice-matched and thermally-matched substrates for further epitaxial growth of high quality GaN with a low dislocation density for advanced heterostructure devices.
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| 2. |
- Janzén, Erik, et al.
(författare)
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Defects in SiC
- 2003
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Ingår i: Physica B: Condensed Matter, Vols. 340-342. - : Elsevier BV. ; , s. 15-24
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Konferensbidrag (refereegranskat)abstract
- Recent results from studies of shallow donors, pseudodonors, and deep level defects in SiC are presented. The selection rules for transitions between the electronic levels of shallow donors in 4H-SiC in the dipole approximation are derived and the ionization energy for the N donor at hexagonal site is determined. Optical and electrical studies of the D-I center reveal the pseudodonor nature of this defect. Defects in high-purity semi-insulating (SI) SiC substrates including the carbon vacancy (V-C), silicon vacancy (V-Si), and (V-C-C-Si) pair are studied. The annealing behavior of these defects and their role in carrier compensation in SI 4H-SiC are discussed. (C) 2003 Elsevier B.V. All rights reserved.
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| 3. |
- Mason, P, et al.
(författare)
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Octupole signatures in Ba-124,Ba-125
- 2005
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Ingår i: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 31:10, s. S1729-S1733
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Tidskriftsartikel (refereegranskat)abstract
- The gamma decay of the nuclei Ba-121,Ba-125 has been investigated with the EUROBALL array, using the reaction Ni-64+Ni-64 at E-beam = 255 and 261 MeV. Six new E1 transitions have been found in the nucleus Ba-125, suggesting a significant role of octupole correlations in the origin of its parity doublets. The J(pi) = 3(-) level of the nucleus Ba-124 has been identified for the first time. Its excitation energy is in very good agreement with a prediction based on a microscopic model including octupole interactions.
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| 4. |
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| 5. |
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| 6. |
- Nguyen, Son Tien, 1953-, et al.
(författare)
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Defects in high-purity semi-insulating SiC
- 2004
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Ingår i: Mater. Sci. Forum, Vol. 457-460. - : Trans Tech Publications Inc.. ; , s. 437-
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Konferensbidrag (refereegranskat)
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| 7. |
- Nguyen, Tien Son, et al.
(författare)
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Defects in semi-insulating SiC substrates
- 2003
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Ingår i: Materials Science Forum, Vols. 433-436. ; , s. 45-50
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Konferensbidrag (refereegranskat)abstract
- Electron paramagnetic resonance (EPR) was used to study defects in semi-insulating (SI) SiC substrates grown by high-temperature chemical vapour deposition (HTCVD) and physical vapour transport (PVT). The C vacancy, Si antisite and several other EPR centers, labelled SI-I to SI-8, were observed in the HTCVD and/or PVT 4H-SiC substrates. Photo-EPR has revealed several deep levels responsible for the SI properties in different types of SI 4H-SiC. Annealing behaviour of the defects and the stability of the SI properties with high temperature annealing were also studied.
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| 8. |
- Nguyen, Tien Son, et al.
(författare)
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Silicon vacancy related TV2a center in 4H-SiC
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 68:20
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Tidskriftsartikel (refereegranskat)abstract
- Electron paramagnetic resonance (EPR) was used to study the T-V2a center in 4H-SiC, which was previously attributed to the isolated Si vacancy but with different charge states: neutral, single negative, and triple negative, corresponding to different spin states S=1, S=3/2, and S=1/2, respectively. The T-V2a EPR spectra observed in dark and under light illumination in as-grown high-purity semi-insulating 4H-SiC in the absence of the negatively charged Si vacancy (V-Si(-)) provide direct evidence confirming the spin triplet (S=1) ground state of the center. A model with a triplet ground state and a singlet excited state is proposed to explain previously obtained results. The T-V2a center can be detected in as-grown material annealed at 1600degreesC.
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| 9. |
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| 10. |
- Zolnai, Z, et al.
(författare)
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Annealing behavior of the carbon vacancy in electron-irradiated 4H-SiC
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 96:4, s. 2406-2408
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Tidskriftsartikel (refereegranskat)abstract
- The annealing behavior of the positively charged carbon vacancy in electron-irradiated 4H-SiC was studied. Electron paramagnetic resonance was used for the purpose of analysis. It was found that around 1000 °C, the EPR signal of the defect starts decreasing. Clear ligand hyperfine structure was also observed after annealing at 1350 °C. Results show that the EI6 center may be the positively charged carbon vacancy at the hexagonal lattice site of 4H-SiC.
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