Enhancement of infrared photo-responses of the Schottky gate region of an n-AlGaAs/GaAs heterojunction FET by a second light illumination

Abstract

Abstract IR photo-responses of the Schottky-barrier gate region are investigated in an n-AlGaAs/GaAs FET. When the Schottky gate region is illuminated by an IR light with the energy above the Schottky barrier, IR photoelectrons are excited and transferred from the gate to the 2D electron gas channel, resulting in the generation of a photocurrent J DG. It is demonstrated that the photocurrent J DG is strongly enhanced, when a weak second light having photon energy above the GaAs band gap locally illuminates the ungated region of the FET; J DG is increased by about three times due to the second light of P 2nd = 0.3 μW, where the increase of J DG is nearly proportional to the second light power P 2nd. The second light effectively enhances the IR photo-response in the Schottky gate region, even though the intensity of the second light is much weaker than that of the IR light, and the irradiated position is far away (~1 mm) from the gate region. Comparing the experimental results with a theoretical model based on the electron drift and hole diffusion, the enhancement mechanism of the photocurrent J DG is clarified.