Intervalley scattering in GaAs and InP probed by pulsed far-infrared transmission spectroscopy

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Abstract
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.