Terminating Structure of Plasma-Assisted Molecular Beam Epitaxial GaN{0001} Film Surface Identified by Coaxial Impact Collision Ion Scattering Spectroscopy

Terminating structures of the GaN{0001} films grown on nitrided sapphire(0001) substrates by plasma-assisted molecular beam epitaxy (MBE) have been investigated by coaxial impact collision ion scattering spectroscopy (CAICISS). The analyses of incidence angle dependences of time of flight (TOF) spectra have shown that the surfaces of GaN films grown under both N-rich and Ga-rich conditions are (0001) N-planes terminated with Ga atoms. This implies that (0001), N-terminated surfaces of GaN films grown under these conditions are unstable and a Ga-rich condition is required to avoid the N-deficiency in the grown GaN film.