PHOTOCURRENT IN A SCHOTTKY-GATED ALGAAS GAAS STRUCTURE WITH A SINGLE-QUANTUM-WELL/

The photocurrent in a Schottky-gated AlGaAs/GaAs structure with a sing le quantum well 5.1 nm thick has been studied. At high negative gate b ias voltages, the effect of the quantum well stems from an increase in the reflectance of the structure in the region of optical transitions between hole and electron subbands. The photocurrent decreases as a r esult. At high positive bias voltages and low temperatures, the predom inant mechanism for the photocurrent is a change in space charge. The quantum well substantially reduces the amplitude of, and alters the el ectrical phase of, the photocurrent because of an absorption of light and a tunneling of charge carriers into the adjacent regions of AlGaAs barriers. At T > 200 K the absorption of light by the quantum well an d the subsequent thermal emission of charge carriers lead to a substan tial increase in the photocurrent. The mechanism for the vertical tran sport involves a thermal emission of electrons from the well and the G aAs buffer layer into the AlGaAs barriers. It also involves the presen ce of trapping centers of the DX-center type in the barriers. Data on the effect of an accumulation of charge carriers and an interference o f light on the photocurrent are reported. (C) 1995 American Institute of Physics.