Direct Subpicosecond Measurement of Carrier Mobility of Photoexcited Electrons in Gallium Arsenide

Abstract

The mobility of hot electrons in gallium arsenide has been measured with subpicosecond time resolution, following injection by 2-eV femtosecond pulses. The mobility immediately after injection was measured to be less than 500 ${\mathrm{cm}}^2$/V.s, indicating efficient electron transfer into the satellite $L$ valleys. The electron mobility then rose to a quasiequilibrium value of 4200 ${\mathrm{cm}}^2$/V.s, limited by electron-hole scattering. The rise time was observed to be between 1.8 and 3.2 ps depending on injected carrier density.