Epitaxial growth of cubic and hexagonal GaN on GaAs by gas‐source molecular‐beam epitaxy

GaN epilayers were grown on GaAs substrates by gas‐source molecular‐beam‐epitaxy technique using dimethylhydrazine as a nitrogen source. It was found that cubic GaN grows on GaAs (001) surfaces epitaxially, while hexagonal GaN grows on GaAs (111) surfaces, from the analyses of x‐ray diffraction and reflection high‐energy electron diffraction patterns. Cathodoluminescence measurements suggested that the band‐gap energy of cubic GaN is around 0.37 eV larger than that of hexagonal GaN.