Surface morphology changes in ZnSe-related II–VI epitaxial films grown by molecular beam epitaxy

Abstract

Surface morphological changes in ZnSe-related II–VI epitaxial films grown by molecular beam epitaxy have been investigated by atomic force microscopy and transmission electron microscopy. We found that under group-II-rich conditions with $\text{c(2×2)}$ surface reconstruction, the process of roughening gives rise to periodic elongated corrugations aligned in the [11̄0] direction. Under group-VI-rich conditions with $\text{(2×1)}$ surface reconstruction, rounded grains form instead of corrugated structures. The surface morphology is dependent on the VI/II ratio and growth temperature, but is independent of the film strain. The observed morphological changes are mainly due to growth kinetics and are not stress driven. We propose a model to explain the changes in surface morphology under group-II-rich conditions and group-VI-rich conditions.