Nucleation and growth mechanisms during MBE of III-V compounds

In this paper we discuss our recent results on the homoepitaxial growth of GaAs from beams of Ga and As-2((4)) and of InAs on GaAs from In and As-2((4 )) beams. Experimental measurements are based on in-situ reflection high en ergy electron diffraction (RHEED) and scanning tunnelling microscopy (STM), while their analysis relies on kinetic Monte Carlo (KMC) simulations and t he application of rate equations. We emphasise the comparative behaviour on all three low-index substrate orientations and the importance of surface r econstruction. Wherever possible we use an atomistic approach and in the ho moepitaxial studies we are principally concerned with nucleation effects oc curring at the sub-monolayer stage, including site-specific adatom incorpor ation and arsenic molecule dissociation pathways, especially the essential requirement of a mobile precursor state. Some results for vicinal plane gro wth are also presented. In the case of the InAs system, we have investigate d strain relaxation processes using STM images, while specifically for grow th on GaAs(001)-2 x 4 and c(4 x 4) surfaces we have studied the formation o f so-called self assembled quantum dots (SADs) in relation to the classical Stranski-Krastanov mechanism and the associated strain effects. Although i t is frequently stated that this accounts fully for dot formation, we have found many anomalies and believe the process, and indeed the final structur es, to be much more complex than generally believed. (C) 1999 Elsevier Scie nce S.A. All rights reserved.