Unusual persistent photoconductivity in the InAs/AlSb quantum well

Unusual features of persistent photoconductivity are reported for the InAs/AlSb quantum-well (QW) structure with a backgate. A negative persistent photoconductivity made it possible to decrease the electron concentration by an order of magnitude from 6 x 10¹¹ cm^-2. This is the largest variation in the electron concentration for this effect. In addition to a pronounced negative persistent photoconductivity, the relaxation of the structural resistance was bistable under exposure of the structure to visible light. These phenomena are attributed to the effect of a thin Ge film deposited on the structure surface prior to photolithography. This film forms a region in the GaSb layer in which the holes are accumulated from the sequence of the Ge/GaSb/AlSb layers located above the QW. IR radiation initiates beats of Shubnikov-de Haas oscillations in the region of weak magnetic fields. These beats are believed to be caused by spin splitting in a zero magnetic field due to the asymmetry of a potential profile of the QW. This asymmetry is induced by prolonged illumination of the structure.