High-temperature annealing of bulk GaN layers

The influence of high-temperature (1010°C) annealing in a flow of gaseous ammonia on the properties of bulk GaN layers, grown by chloride-hydride VPE and then separated from SiO2 substrates, was studied using atomic force microscopy. The bulk (∼360-μm-thick) epitaxial GaN layers were synthesized in two steps: a first stage of nucleation and growth at a low temperature (530°C) followed by epitaxy at a high temperature (970°C). It was found that the annealing increases the nanorelief height and activates the donor-acceptor recombination on the surface of a GaN layer grown at the lower temperature and decreases the intensity of photoluminescence from the layer grown at the higher temperature.