Negative photoconductivity of two-dimensional holes in GaAs/AlGaAs heterojunctions

Abstract
A negative photoconductivity is observed due to the two-dimensional (2D) holes at GaAs/Al0.5Ga0.5As heterojunctions under illumination by a red light-emitting diode below ∼6 K. The photoconductivity follows a nonexponential decay after the illumination is turned off. Quantum transport measurements are made to demonstrate explicitly that the photoconductivity is due to a decrease in the density and mobility of the 2D holes, and a model is proposed to explain the phenomenon.