Evidence of a mobility edge in the second subband of anAl0.33Ga0.67As-GaAs heterojunction

Abstract
We report on simultaneous measurements of mobility and Dingle temperature of a two-dimensional electron gas in an AlGaAs/GaAs heterojunction, the density of which is varied by means of infrared illumination. Detailed measurements reveal that the Dingle temperature of the first subband decreases abruptly as a function of density when the second subband becomes occupied but the accompanying drop in mobility occurs smoothly over a broader density interval. We interpret these results as indicating the existence of a mobility edge at the bottom of the second subband.