Hexagonal growth hillocks of MOCVD-grown GaN on (0001) sapphire

摘要

Hexagonal growth hillocks in GaN epilayers grown by MOCVD on sapphire have been studied by scanning electron (SE), atomic force and optical microscopy. The SE micrographs obtained at incident electron energies >= 15 keV show pyramid-like and plate-like hillocks of hexagonal cross-section, while smaller hexagonal holes/pittings are observed at lower incident electron energies. Again at the lower electron energies, some of the plate-like hexagonal hillocks disappear from the image, leading us to surmise that these features are sub-surface. Monte-Carlo simulations of electron beam solid interactions provide a way of interpreting the SEM images.