Experimental and Theoretical Analysis of Photocurrents in GaAs MESFETs Operated in Normally off Mode

Optical control of microwave devices, particularly MMIC, is a rapidly growing research area. This paper presents a theoretical analysis, which accurately predicts the photocurrents of MESFETs operated in normally OFF mode. The model accounts for the variation of the intensity and wavelength of the incident light. The analysis includes both photovoltaic and photoconductive effects. The photocurrent in the semi-insulating substrate under the gate depletion region is considered. The leakage current between the drain and source bonding pads via the substrate is also included in the model. Good agreement is realized between measured and calculated results. The model can be used as a tool for the optimal design of MESFET optical detectors.