Surface morphology of homoepitaxial GaSb films grown on flat and vicinal substrates

We have compared the surface morphology of GaSb homoepitaxial films grown on both flat and 1° vicinal [miscut towards (111)A] (001) substrates using atomic force microscopy and scanning tunneling microscopy. Mound formation is observed for GaSb homoepitaxy on the flat substrates over a range of growth temperatures when either Sb2 or Sb4 is used to supply the group V flux. At sufficiently high growth temperatures, which are different depending on whether Sb2 or Sb4 is used, the mounds transform into fairly well-defined pyramids comprised of distinctly stacked layers that are clearly separated by monolayer-height steps. Furthermore, at the tops of the pyramids are sharp, tower-like features that are ∼15Å in height. Mounds also appear during homoepitaxy on the vicinal substrates at lower growth temperatures; however, both mounds and pyramids can be suppressed when using either Sb2 or Sb4 by growing at temperatures above ∼400°C. We discuss and compare qualitatively the shape of the observed mounds with predictions of evolving morphology based on models of unstable epitaxial growth.