Hot electron relaxation time in GaN

The hot electron relaxation time is studied in an n-type GaN film grown by molecular beam epitaxy on sapphire. A femtosecond pump–probe technique is used in which the electrons are excited by an infrared pump and the carrier dynamics are monitored by a tunable near ultraviolet probe. Complex transients, showing bleaching or induced absorption, are observed. The data are fitted by a model in which the longitudinal optical (LO)-phonon emission is the dominant energy relaxation process. The LO-phonon emission time is measured to be 0.2 ps.