Time-resolved experimental study of carrier lifetime in GaN epilayers

Time-resolved photoluminescence and light-induced transient grating measurements of GaN epilayers show that the photoluminescence decay can be described by two coupled exponential terms and that carrier mobility and lifetime in GaN epilayers are correlated within the model which accounts for nonradiative carrier recombination predominantly at dislocations. The obtained results demonstrate that migration-enhanced metalorganic chemical vapor deposition (MEMOCVD™) allows for growth of high-quality GaN epilayers on sapphire substrates with the dislocation density close to 108cm−2, carrier lifetime as long as 2 ns, and ambipolar diffusion coefficient of 2.1cm2s−1 corresponding to the hole mobility of approximately 40cm2V−1s−1.