Wetting of GaN islands by excess Ga: Origin of different appearances of GaN islands in scanning tunneling microscopy

Abstract

We observe three different kinds of islands, namely the bare, ghost, and normal islands, by scanning tunneling microscopy of GaN(0001) prepared under Ga-rich conditions with different excess Ga coverage. They correlate to three different growth regimes. The various morphologies of the islands are suggested to be due to different states of wetting of the surface by excess Ga. The dynamical behavior of the wetting process is followed, and an island size dependence of Ga wetting is noted.