Surface states and surface oxide in GaN layers

Surface photovoltage spectroscopy, photoluminescence, Auger electron spectr oscopy and x-ray photoelectron spectroscopy were used to correlate the chem ical changes induced by HCl etching of GaN surface to changes in the yellow luminescence related states, through their manifestation in surface photov oltage. The results show a correlation between a removal of the gallium oxi de from the surface and a reduction of the yellow luminescence related tran sition in the surface photovoltage spectra. Based on this observation, it i s suggested that the well known yellow luminescence is emitted from surface states associated with the gallium oxide that decorates the free surface a nd possibly also the substrate interface and internal grain boundaries. (C) 2001 American Institute of Physics.