Evaluation of the surface stoichiometry during molecular beam epitaxy of cubic GaN on (001) GaAs

We use in situ reflection high-energy electron diffraction to investigate the growth kinetics of cubic (001)-GaN/GaAs grown by plasma-assisted molecular beam epitaxy. We find that the GaN surface exhibits three surface reconstructions having (1×1), (2×2), and c(2×2) symmetries, which correspond to Ga adatom coverages of 0, 0.5, and 1, respectively. We demonstrate that the transient behavior of the half-order streak intensity is a sensitive probe of the surface stoichiometry during growth. Particularly, these measurements enable us to directly determine the effective N flux incorporated into the crystal.