M. Betz et al., Ultrafast electron-phonon scattering in semiconductors studied by nondegenerate four-wave mixing, PHYS REV B, 60(16), 1999, pp. R11265-R11268
Nondegenerate four-wave-mixing allows one to monitor the femtosecond relaxa
tion of free carriers in GaAs and CdTe at densities as low as 2 x 10(15) cm
(-3). The energy relaxation time of electrons via LO-phonon emission is det
ermined to be 240 +/- 20 fs in GaAs. In more polar CdTe, this time constant
is found to be as short as 70 +/- 15 fs which is even shorter than the pho
non oscillation period of 200 fs. [S0163-1829(99)51840-7].