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- Darakchieva, Vanya, 1971-, et al.
(författare)
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Anisotropic strain and phonon deformation potentials in GaN
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:19, s. 195217-
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Tidskriftsartikel (refereegranskat)abstract
- We report optical phonon frequency studies in anisotropically strained c -plane- and a -plane-oriented GaN films by generalized infrared spectroscopic ellipsometry and Raman scattering spectroscopy. The anisotropic strain in the films is obtained from high-resolution x-ray diffraction measurements. Experimental evidence for splitting of the GaN E1 (TO), E1 (LO), and E2 phonons under anisotropic strain in the basal plane is presented, and their phonon deformation potentials c E1 (TO), c E1 (LO), and c E2 are determined. A distinct correlation between anisotropic strain and the A1 (TO) and E1 (LO) frequencies of a -plane GaN films reveals the a A1 (TO), b A1 (TO), a E1 (LO), and b E1 (LO) phonon deformation potentials. The a A1 (TO) and b A1 (TO) are found to be in very good agreement with previous results from Raman experiments. Our a A1 (TO) and a E1 (LO) phonon deformation potentials agree well with recently reported theoretical estimations, while b A1 (TO) and b E1 (LO) are found to be significantly larger than the theoretical values. A discussion of the observed differences is presented. © 2007 The American Physical Society.
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| 2. |
- Darakchieva, Vanya, 1971-, et al.
(författare)
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Phonons in strained AlGaN/GaN superlattices
- 2007
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Ingår i: 6th International Symposium on Blue Laser and Light Emitting Diodes,2006. - Physica Status Solidi, vol C4 : WILEYVCH Verlag GmbH & Co. KGaA. ; , s. 170-
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Konferensbidrag (refereegranskat)
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| 5. |
- Paskova, Tanja, 1961-, et al.
(författare)
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Effect of sapphire-substrate thickness on the curvature of thick GaN films grown by hydride vapor phase epitaxy
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 102:12
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Tidskriftsartikel (refereegranskat)abstract
- The effect of sapphire-substrate thickness on the curvature and stress in thick hydride vapor phase epitaxial GaN films was studied by high-resolution x-ray diffraction at variable temperatures. The curvature was found to have the maximum value for comparable thicknesses of the film and the substrate, while the stress at the film surface decreases with increasing film thickness and increases with increasing substrate thickness, which is in very good agreement with the simulation results. The curvature at the growth temperature was found to be strongly influenced by the value of the intrinsic tensile strain, which is determined by the film/substrate thickness ratio. © 2007 American Institute of Physics.
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