Step bunching and step equalization on vicinal GaAs(001) surfaces

Abstract

Terrace width distributions have been calculated from scanning tunneling microscopy (STM) images of molecular-beam epitaxy (MBE)-grown GaAs(001) surfaces misoriented by both 1° and 2° towards the (111)A direction. This analysis reveals a peak in the terrace width distribution at approximately 40–50 Å, regardless of the original miscut, with larger terraces forming in order to preserve the angle of vicinality. Growth of a tilted superlattice (TSL) improves the periodicity of the surface. A statistical analysis of the STM image of a 1° TSL capped with three monolayers of GaAs reveals a bell-shaped distribution of terrace widths with a peak at the average terrace width. These results suggest that MBE growth of vicinal GaAs(001) does not result in equalized steps but that the growth of a TSL does tend towards step equalization. The differences between these two growth regimes are discussed.