Dynamics of extreme nonequilibrium electron transport in GaAs

Hot electron effects have been observed in semiconductors for many decades; however, until recently, direct experimentally determined spectroscopic information on the hot electron distribution function did not exist. As a result the microscopic basis for hot electron transport could only be inferred. To bridge the gap between theory and experiment we invented hot electron spectroscopy, a technique which enabled us to obtain direct spectroscopic information on the electron momentum distribution,n(p). In this paper we describe the technique and discuss hot electron spectra obtained in GaAs. "Ballistic" electron transport is observed in samples having narrow transit regions (1700 Å). In addition, a theoretical model has been developed enabling us to identify all observed features in the spectra.