Thermally activated negative photoconductivity below 6 K in p-GaAs/Al0.5Ga0.5As heterostructures and the effect of uniaxial compression

Thermally activated negative photoconductivity is observed in p-GaAs/Al_0.5Ga_0.5As:Be heterostructures under illumination with red light at temperatures below 6 K. As the temperature decreases, the concentration and mobility of 2D holes in the quantum well drop sharply, particularly under uniaxial compression. The phenomenon is quantitatively described under the assumption that a layer of deep donor-like traps with a low thermal activation barrier E_B = 3.0 ± 0.5 meV exists at a distance of about 7 nm from the heterojunction and that this barrier does not change with strain. Presumably, the traps may be the p-type dopant Be atoms diffusing from the active layer and occupying interstitial positions.