Effective Mg activation for p-type GaN in mixed gas ambient of oxygen and nitrogen

The effects of mixed gas annealing ambient of O2 and N2 on electrical and optical characteristics of p-type Mg-doped GaN grown by MOCVD were investigated at various annealing condition. A mixed gas ambient of 80% O2 and 20% N2 at 750°C for 2 minutes was found to be an optimum annealing condition with improvements on activation efficiency of Mg acceptor compared with annealing in pure O2 or N2 gas ambient. The accompanied results from Hall Effect and photoluminescence measurements of the samples were attributed to the formation of Mg-H and MgGa-VN complexes which caused the Mg passivation; we concluded that the existence of N2 in the annealing ambient can only reduce but not prevent the formation of nitrogen vacancies during high temperature.