Theory of Point Defects Dynamics, Interface Disordering, and Interface Formation in Semiconductors.
Final rept. 15 Dec 92-14 Dec 95,
NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF PHYSICS
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This grant was used to support research on 1 donor-induced interdiffusion in GaAsAlAs super-lattices, 2 the structure and adatom diffusion on the stepped Si100 surface, and 3 the development a new, real-space multigrid method for electronic structure calculations. In GaAs, we used ab initio molecular dynamics to map out the diffusion process. Several competing pathways, involving either vacancies or interstitials, were considered. The results provide a microscopic picture of Si motion in both GaAs and AlAs and of the interdiffusion process. We have also developed a formalism that allows for calculations of free energy differences, and resolved an important controversy regarding the Ga vacancy in GaAs. On the Si100 surface, we investigated the atomic and electronic structure of step edges by an ab initio method for the first time. Our simulated STM images are in very good agreement with experimental data, but change their interpretation. The diffusion paths and barried for adatoms across the buckled and stepped surface were determined. Finally, the real-space multigrid method is particularly suitable for very large scale calculations. The calculations use a grid as a basis and employ multigrid techniques, which results in preconditioning and convergence acceleration at all length scales.
- *POINT DEFECTS
- EXPERIMENTAL DATA
- GALLIUM ARSENIDES
- ALUMINUM ARSENIDES
- MOLECULAR PROPERTIES
- FREE ENERGY
- ATOMIC STRUCTURE
- Electrical and Electronic Equipment