Mobility degradation in a quantum well heterostructure of a GaAs/AlGaAs prototype

Mobility degradation of a quasi-two-dimensional electron gas in a high electric field as shown to arise from the asymmetry in the distribution function of electrons. The critical field for the onset of appreciable mobility degradation is given by ε*=kBT/el=vsat/2μ0, where T is the lattice temperature, l the mean free path, μ0 the low field ohmic mobility, and vsat the saturation velocity. High mobility materials are vulnerable to mobility degradation particularly at low temperature. The effective electron temperature in a protruded distribution undergoes a transition from quadratic to linear behavior as the electric field is increased. This behavior is consistent with the most recent experimentally observed behavior of GaAs/AlGaAs heterostructures and can be usefully applied to the design of devices operating at high electric field.