Accession Number : ADA315864

Title :   Theory of Point Defects Dynamics, Interface Disordering, and Interface Formation in Semiconductors.

Descriptive Note : Final rept. 15 Dec 92-14 Dec 95,

Corporate Author : NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF PHYSICS

Personal Author(s) : Bernholc, J.

PDF Url : ADA315864

Report Date : OCT 1996

Pagination or Media Count : 11

Abstract : This grant was used to support research on (1) donor-induced interdiffusion in GaAs/AlAs super-lattices, (2) the structure and adatom diffusion on the stepped Si(100) 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 Si(100) 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.

Descriptors :   *INTERFACES, *SEMICONDUCTORS, *POINT DEFECTS, ELECTRONICS, EXPERIMENTAL DATA, COMPUTATIONS, DYNAMICS, ACCELERATION, GALLIUM ARSENIDES, GRIDS, PATHS, IMPURITIES, INTERSTITIAL, MICROSCOPY, SCALE, LENGTH, BUCKLING, CONVERGENCE, ALUMINUM ARSENIDES, DIFFUSION, PICTURES, MOLECULAR PROPERTIES, FREE ENERGY, ATOMIC STRUCTURE, ADATOMS.

Subject Categories : Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE