| 1. |
- Hultquist, Gunnar, et al.
(author)
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Influence of deuterium and platinum on the thermal oxidation of GaAs
- 2003
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In: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 150:10, s. G617-G623
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Journal article (peer-reviewed)abstract
- The thermal oxidation of GaAs at 500 degreesC in O-18 labeled O-2 has been studied with gas phase analysis, Auger electron spectroscopy, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy. The influence of a few hundred atomic parts per million of deuterium in the GaAs substrate and of surface platinum have been evaluated with respect to oxide growth mechanisms and the degree of As buildup. Deuterium increased the transport from the substrate interface of both Ga and As toward the gas interface thereby lowering the degree of preferential Ga oxidation and As buildup at the substrate interface. Platinum, on the other hand, catalyzed the dissociation of the oxygen molecule at the gas interface and thereby facilitated an increased transport of oxygen toward the substrate interface. That results in an increased overall oxidation rate with a high degree of preferential Ga oxidation and concomitant As buildup. When the oxygen pressure was increased from 20 to 720 mbar, a lowered degree of As buildup was observed due to the lower degree of preferential Ga oxidation.
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| 2. |
- Mathieu, R, et al.
(author)
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Magnetization of ultrathin (Ga,Mn)As layers
- 2003
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In: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 68:18: 184421
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Journal article (peer-reviewed)abstract
- Kerr rotation and superconducting quantum interference device magnetometry measurements were performed on ultrathin (Ga0.95Mn0.05)As layers. The thinner layers (below 250 A) exhibit magnetic properties different than those of thicker ones, associated with different microstructure, and some degree of inhomogeneity. The temperature dependence of the field-cooled magnetization of the layers is recorded after successive low temperature annealings. While the Curie temperature of the thicker layer (250 A) is nearly unchanged, the critical temperature of the thinner layers is enhanced by more than 23 K after two annealings. Secondary ion mass spectrometry experiments on similar layers show that Mn is displaced upon annealing. The results are discussed considering a possible segregation of substitutional and interstitial Mn atoms at the surface of the (Ga,Mn)As layers.
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| 3. |
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| 4. |
- Paskova, Tanja, et al.
(author)
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Growth and separation related properties of HVPE-GaN free-standing films
- 2002
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In: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 246:3-4, s. 207-214
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Conference paper (other academic/artistic)abstract
- Hydride vapour phase epitaxial GaN layers with thicknesses in the range 10-150µm grown directly on sapphire or using metalorganic vapour phase deposited GaN templates have been separated by laser-induced lift-off technique. Both faces of the free-standing films have been studied by photoluminescence and high-resolution X-ray measurements and stress analysis has been performed. A comparison with as-grown films reveals the changes in the properties of the material after the separation process. The separation conditions are found to be responsible for the bowing in the free-standing GaN films while the type and intensity of emission bands, as well as defect and impurity distributions are related only to the growth conditions. The residual strain in the free-standing layers is attributed to both non-optimized separation conditions and non-uniform defect density in the films. © 2002 Elsevier Science B.V. All rights reserved.
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| 5. |
- Paskova, Tanja, et al.
(author)
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Mass transport growth and properties of hydride vapour phase epitaxy GaN
- 2001
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In: Physica status solidi. A, Applied research. - 0031-8965 .- 1521-396X. ; 188:1, s. 447-451
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Journal article (peer-reviewed)abstract
- We report a comparative study of the optical and structural properties of mass-transport and conventionally grown GaN by hydride vapor phase epitaxy. A strong donor-acceptor pair emission is observed from the mass-transport regions with a distinctive intensity contrast between the exciton and donor-acceptor bands from mass-transport and nontransport regions. Secondary ion mass spectroscopy was employed to investigate the impurity incorporation into different regions. A moderate increase of residual impurity incorporation or redistribution was found in mass-transport regions related to different growth modes.
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| 6. |
- Peto, G, et al.
(author)
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Formation of epitaxial CoSi2 films on Si and on Si/Si80Ge20 (100) by reactive deposition epitaxy
- 2002
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In: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 81:1, s. 37-39
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Journal article (peer-reviewed)abstract
- CoxTi1-x layers were deposited on Si (100) and on Si/Si80Ge20 (100) capped with 30- or 40-nm-thick Si at 650 degreesC substrate temperature at 1x10(-6) Pa pressure. The Co-silicide films grown by reactive deposition epitaxy were characterized by Rutherford backscattering-channeling, x-ray difraction, by depth profile analysis of the components, and by sheet resistance measurements. The Ti content of the deposited Co layers was between 0.1 and 8 at. %. The epitaxy of the layers on Si and on Si/Si80Ge20 improved by increasing the Ti concentration. The minimum yield of the channeling and the full width at half maximum value of the rocking curve of CoSi2 decreased. The sheet resisitance of the formed layers was also minimal in these cases. The method applied is promising to form epitaxial CoSi2 layers on SixGe1-x substrates.
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