The oxidation of gallium nitride epilayers in dry oxygen

The oxidation of GaN epilayers in dry oxygen has been investigated. The GaN epilayers, about 1 mum thick, were grown on (0001) sapphire substrates by rapid thermal process/low pressure metalorganic chemical vapor deposition. Bulk theta - 2 theta X-ray diffraction (XRD) data showed that the slight ox idation of GaN began to occur at 800 degreesC for 6 h. The oxide was identi fied as the monoclinic beta -Ga2O3. The GaN epilayers were completely oxidi zed at 1050 degreesC for 4 h or at 1100 degreesC for 1 h. For all samples, the strongest oxide's peak is (11-3), and (30-6) followed. There is a rapid oxidation process in the initial stage of oxidation, and a relatively slow process followed when the temperature was over 1000 degreesC. The oxidatio n of two stages was limited by the rate of an interfacial reaction mechanis m and by the diffusion mechanism, respectively. When the temperature reache s 1100 degreesC, the oxidation rate is very fast, which is considered as th e results of the GaN decomposition at high temperature under atmosphere. Th e oxide layers were also observed by a scanning electron microscope, which shows a rough oxide surface and an expansion of the volume of 40%. The phot oluminescence (PL) seriously influenced by the oxidation is also discussed.