Hot-electron relaxation in GaAs quantum wells

We report experiments in which we determine the rate of LO-phonon emission by hot electrons. High-energy tails of the photoluminescence spectra are used to measure the distributions of hot electrons, which are heated both optically and electrically. Comparison of resultant temperatures shows that virtually all the excess kinetic energy of an optically excited electron-hole pair stays in the electron system. Both this result and an analysis of the spectra themselves show that electron scattering is much faster than LO-phonon emission. The measured LO-phonon emission rate is in agreement with theory. Hot phonons do not appear to play an important role in our experiments.