Persistent photoconductivity in p-type Al0.5Ga0.5As/GaAs/Al0.5Ga0.5As heterostructures

Illumination of a double p-Al0.5Ga0.5As/GaAs/Al0.5Ga0.5As heterostructure by a red light-emitting diode results in a negative photoconductivity that, after the diode is switched off, slowly relaxes to a positive persistent photoconductivity (PPPC), characterized by about a 1.5 times increase of two-dimensional hole concentration and a 1.7 times increase of mobility in comparison with the initial state in the dark. This metastable state may be explained in the framework of the model in which deep electron traps are supposed to be located above the Fermi level on the inverted heterointerface. The calculated concentration of interface charges reveals a 2.4 times decrease between the dark and PPPC states that is in qualitative agreement with the assumed model.