Keywords:semiconductor, field effect transistor, photocurrent
We investigated infrared (IR) photo-responses of the Schottky-barrier gate region of an n-AlGaAs/GaAs field effect transistor (FET) and found that the photocurrent from the channel region to the gate is strongly enhanced when a weak second light having photon energy above the GaAs bandgap illuminates the FET locally. The photocurrent is increased by about 3.4 times by the second light. The enhancement effect is nearly independent of the illumination position of the second light, and remains even when the illumination position is far away from the gate. The experimental findings are compared with a theoretical model based on the electron drift and hole diffusion.