GaN layers grown directly onto GaAs by molecular beam epitaxy

GaN layers were grown by radio-frequency nitrogen plasma source molecular beam epitaxy onto both (001) and (111) GaAs wafers. The deposition temperature was varied from 500°C up to 730°C. GaN layers grown on (111) GaAs are hexagonal with columnar morphology. The growth onto (001) GaAs results in hexagonal layers under nitrogen-rich conditions, while cubic GaN layers are grown at a stoichiometric N/Ga ratio. The grown layers are studied by transmission electron microscopy in cross section. The orientation relationships are determined.