Enhanced Layer Growth of GaAs: Sn

Abstract

We have investigated the surface morphology of GaAs(100) during growth by molecular beam epitaxy in the presence of submonolayer coverages of Sn. Sn submonolayers segregate to the surface during growth and cause the measured reflection high-energy electron diffraction, intensity oscillations to continue long past that observed on pure GaAs. Atomic force microscopy in air and scanning tunneling microscopy have been used to examine these surfaces prior to growth, during growth, and after heating in vacuum in order to determine the changes in surface morphology contributing to this behavior. The major role of the Sn coverage is to remove the surface anisotropy usually observed in GaAs(100) growth and to increase the stability of islands. The strain induced by Sn in substitutional Ga sites destabilizes these islands and tends to limit their size. During growth, nucleation on these small islands is less likely, leading to an enhancement in the layer growth.