Deep levels in GaN grown by nitridation of GaAs (110) surface in a electron cyclotron–resonance ammonia plasma

Abstract

The native defects in GaN synthesized by the nitridation of GaAs surfaces (1 1 0) in electron–cyclotron resonance-induced ammonia plasma have been monitored by using a thermally stimulated exo-electron emission spectroscopy. A pair of defects separated by an energy 0.04 eV have been identified in the films deposited for varying periods of time. The average energies of these two defect levels were found to be 0.59 and 0.64 eV. They have been correlated to the E2 and E3 levels in GaN, respectively, as reported by earlier workers. Stoichiometry of the nitrided films was studied by X-ray photoelectron spectroscopy; which was found to be uniform throughout the nitrided region. The films showed broad photoluminescence spectra centered at 360 nm and a tailing part towards longer wavelength. This feature has been explained to arise from the existence of the mixed phases under the existing plasma conditions. Scanning electron microscopy and atomic force microscopic studies showed that the film consisted of nanocrystalline globules with average grain size of 50 nm.