Surface orientation dependent surface kinetics and interface roughening in molecular beam epitaxial growth of III–V semiconductors: A Monte Carlo study

Abstract

A framework for examining molecular beam epitaxial (MBE) growth of lattice-matched III–V compound semiconductors is presented. It accounts for the basic kinetic parameters such as surface orientation and local environment dependent sticking coefficients, surface migration, and evaporation rates. Monte Carlo computer simulations are employed to examine the influence of these and other features—such as the molecular nature of the group V beam commonly employed—on the nature of the growth mechanism and the resulting interface profile. The [100] growth is found to exhibit a change from the two-dimensional nucleation and (consequently, layer-by-layer) growth mechanism to a three-dimensional nucleation mechanism with increasing growth temperature, thus exhibiting interface roughening. This interface roughening is, however, critically controlled by the surface geometry dependent surface migration kinetics. It is thus fundamentally distinct from the surface roughening transition predicted by Burton, Cabrera, and Frank which is independent of the kinetics and caused by the thermodynamic fluctuations at equilibrium. Recent studies of GaAs/AlGaAs [100] growth revealing the occurrence of interface roughening above a certain temperature, if intrinsic, we propose corresponds to the kinetically controlled surface roughening predicted by the present simulations, rather than to the surface roughening transition of Burton, Cabrera, and Frank as suggested by other investigators. The [110] growth, in the absence of exchange reactions, is found to exhibit the layer-by-layer growth mechanism over the commonly employed growth temperature regime. Consequently, the results predict that occurrence of rough interfaces for the [110] growth of systems such as GaAs/AlGaAs is primarily a consequence of exchange reactions induced during the deposition process. The geometry of the [110] growth front reveals such exchange reactions to be far more facile due to the expected lower activation barriers for exchange as well as for the surface migration processes of relevance. The implications of these results for understanding the [110] growth of GaAs/AlxGa1−xAs system are explored.