INTERVALLEY SCATTERING IN GAAS AND INP PROBED BY PULSED FAR-INFRARED TRANSMISSION SPECTROSCOPY

The dynamics of photoexcited electrons in GaAs and InP were studied using the transmission of 200-fs pulses of far-infrared radiation in the spectral range 15-100 cm-1. Kinetic traces of the infrared transmission as a function of delay between optical excitation and infrared probe show a probe-limited decrease in transmission followed by a more gradual (0.7-2 ps) drop to a steady value, consistent with the slow return of electrons from high-mass satellite valleys. Infrared transmission spectra, analyzed in the context of a Drude model, reveal density-dependent electron mobilities 3-4 times below equilibrium n-doped values. Electron-hole collisions likely account for the lower mobility.