Changes in surface composition of GaN by impurity doping

Changes in the surface composition of GaN films by p- and n-type doping were studied using both Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). It was found that the surface composition of the GaN films was affected by impurity doping, i.e. the surface of the p-type GaN film was enriched with gallium and that of the n-type GaN him with nitrogen, compared with that of the undoped GaN him. The surface composition of the GaN films by AES agrees with that by XPS after taking the contamination layer thickness into account. The experimental results thus obtained were discussed by taking account of the formation energies of native defects in p- and n-type GaN.