Optical High-Field-Transport Experiments in GaAs Quantum Wells.

We review three recent experiments in which we have used optical techniques to investigate quantities relevant to high field transport in semiconductors. We will discuss (1) a measurement of drift velocity of minority carriers in GaAs quantum wells by a time-of-flight technique, (2) a simultaneous measurement of the luminescence spectra which allows us to determine the carrier distribution function and investigate the energy exchange rate between electrons and holes, and (3) an optical imaging experiment which demonstrates the existence of negative absolute mobility for the minority carriers in modulation-doped quantum wells. The momentum scattering rate between electrons and holes is determined from this experiment.