ENHANCEMENT OF ALLOY SEGREGATION DUE TO STRAIN ASSISTED ATOMIC DIFFUSION IN HETEROEPITAXY

Strain fields have proved to play a very important role in the self-or ganization of 3D islands which appear during highly mismatched epitaxy (e.g. for InAs deposited on GaAs, or SiGe/Si), In this work we focus on stress-driven atomic exchanges in inhomogeneously strained systems in order to derive - from a self consistent treatment - the stable equ ilibrium atomic distribution. For this we first calculate the energy o f an atom, as a function of the local average strain. Then we combine this relation with the strain distribution calculated for a starting a tomic configuration using a valence force field approach. Surface effe cts are also taken into account in a simple way, This study applies to alloy segregation in 3D quantum boxes before, as well as during, thei r burying process, or to alloy segregation due to surface roughening d uring the deposition of very thick lattice-matched alloy 2D layers. So me results are compared with recent experimental observations of surfa ce segregation in (Ga, In)As/GaAs quantum boxes. (C) 1998 Elsevier Sci ence B.V.