An investigation into the early stages of oxide growth on gallium nitride

The early stages of thermal oxidation of gallium nitride epilayers in dry O 2 have been studied using surface sensitive analytical techniques and transmission electron microscopy. Deconvolution of the Ga 3d core level spectra from X-ray photoelectron spectroscopy revealed peak positions representing gallium nitride, gallium oxide, and an intermediate phase. Transmission electron microscopy revealed an overlayer approximately 1.5–3.0 nm thick with registry to the (0001) GaN after dry oxidation at 800°C for 1 h. Based on the data from X-ray photoelectron spectroscopy, this layer is believed to be a Ga ( x+2) N 3 x O (3−3 x) compound. Atomic force microscopy and transmission electron microscopy revealed the formation of discrete oxide crystallites on top of the oxynitride layer. The crystallites become more numerous and grow with continued oxidation.