The dynamical transition to step-flow growth during molecular-beam epitaxy of GaAs(00l)

Abstract

Scanning tunneling microscopy studies have been performed on GaAs homoepitaxial films grown by molecular-beam epitaxy. Images show that in the earliest stages of deposition the morphology oscillates between one with two-dimensional islands and flat terraces. After the initial transient regime, the system evolves to a dynamical steady state. This state is characterized by a constant step density and as such the growth mode can be termed step flow. Comparison with RHEED shows that there is a direct correspondence between the surface step density and the RHEED specular intensity. Furthermore, thick films (up to 1450 monolayers) display a constant or slowly increasing surface roughness consistent with long adatom diffusion lengths and limited upward diffusion.