Preparation of stoichiometric GaN(0 0 0 1)-1 × 1 studied with spectromicroscopy

Using annealing in an ammonia atmosphere in combination with Ga adsorption and desorption, polar surfaces of ex situ grown GaN(0 0 0 1) epilayers can be prepared towards clean and stoichiometric conditions. This combination of surface treatments also improves the surface crystalline order and chemical homogeneity, as observed in photoelectron spectra, in low energy electron diffraction (LEED) patterns, and of the coefficient of variation (Cvar) of the Ga 3d intensity in the spectromicroscopy images. The lateral resolution limit of the spectromicroscopy images is 2 μm. The surface improvements during NH3 annealing show saturation effects. The best surface quality in terms of the crystalline order and chemical homogeneity was found after annealing at 800 °C in NH3, followed by Ga adsorption and finally desorption by annealing in a NH3 atmosphere.