Mixing mechanism of h-GaN in c-GaN growth on GaAs (001) substrates

Systematic investigation of the V/III ratio dependence in the mixing of the h-GaN phase to the c-GaN layers grown on GaAs (001) substrates has been performed and a drastical change of the mixing nature in the initial process is reported. The h-GaN mixing nature on the {111} facets during growth strongly depends on the V/III ratio in the initial buffer layer formation. The h-GaN grain-mixing only occurs on (111)A facets under a Ga-rich formation condition, but the h-GaN mixing grains on the {111}B facets gradually appear together with the vanishing of h-GaN grains on the {111}A facets during the annealing process under rf-nitrogen beam irradiation. The mixing processes under N-rich and Ga-rich growth conditions are also discussed. The results indicate that it is possible to grow high quality c-GaN layers by control of the mixing at the initial growth stage through the effective V/III ratio dependence.