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.

• Received 14 January 1987

DOI:https://doi.org/10.1103/PhysRevLett.58.2355