Persistent photoeffects in p-i-n GaAs/AlGaAs heterostructures with double quantum wells

Abrupt changes in the capacitance between the p and n regions were observed in a planar p-i-n GaAs/AlGaAs heterostructure with two tunneling-coupled quantum wells exposed to laser irradiation (lambda = 633 nm). These changes can be caused by variations in both temperature (in the vicinity of T similar to 2 K) and the dc voltage applied to the structure. A memory effect was detected; this effect manifested itself in the long lifetime of anomalies observed after the illumination had been turned off. Self-consistent calculations of distributions of charge and electric field were performed for the structures that contained a donor impurity in AlGaAs layers; this impurity is responsible for origination of DX centers that give rise to persistent photoconductivity. It is demonstrated that abrupt changes in capacitance can occur in such a structure, and the values of the parameters required for origination of these jumps are determined.