Electron and hole dynamics in GaN

The hot electron and hot hole dynamics have been studied in n-type and p-type GaN films grown by molecular beam epitaxy on sapphire. A novel non-degenerate femtosecond pump-probe spectroscopic technique has been used, in which the electrons (or holes) are excited by a strong infrared pump, and carrier thermalization and cooling are monitored by a tunable UV probe. From the complex transients, which show bleaching and induced absorption, we have been able to determine several parameters of importance, including the hot electron and the hot hole relaxation times. The experimental results are compared to the theoretical predictions obtained assuming that LO-phonon emission is the dominant energy relaxation process.