Surface diffusion length of Ga adatoms on (111)B surfaces during molecular beam epitaxy

Abstract

The spatial variation of the growth rate on mesa-etched GaAs (1̄1̄1̄)B substrates during molecular beam epitaxy of GaAs is measured from the period of the reflection high-energy electron diffraction (RHEED) intensity oscillation using in situ scanning microprobe RHEED. The surface diffusion length of Ga adatoms on the (1̄1̄1̄)B surface is determined from the spatial variation of the growth rate. The surface diffusion length on the (1̄1̄1̄)B surface increases as the substrate temperature is raised or the arsenic pressure is decreased. The typical value of the diffusion length is about 10 μm at a substrate temperature of 580 °C and an arsenic pressure of 5.7×10−4 Pa, which is an order of magnitude larger than that on the (100) surface along the [011] direction. The activation energy of the surface diffusion length changes with the surface reconstruction. Anisotropic diffusion, as reported for the (100) surface, is not observed on the (1̄1̄1̄)B surface.