Hot carriers in quasi-2-D polar semiconductors

This paper reviews hot carrier effects in quasi-2-D polar semiconductors (quantum wells and heterostructures), with special emphasis on the GaAs/AlGaAs system. After briefly introducing the basic concepts in hot carrier physics, we discuss theoretical calculations of carrier-phonon interactions and hot carrier energy loss rates to the lattice in quasi-2-D systems. We then discuss how these quantities are affected by degeneracy, plasma effects, and hot phonons. The bulk of the paper is devoted to a discussion of experimental results and their analysis. Three kinds of experiments are discussed: I-V and related transport measurements, direct time-of-flight measurements of velocity-field characteristics, and measurements which use optical spectroscopy to provide direct information about the carrier distribution function in the presence of external perturbations. The optical studies have given valuable new insight into the behavior of hot carrier relaxation processes in quasi-2-D systems from femtosecond to steady-state conditions.