Model for illumination-dependent trap occupancy in optically biased GaN metal-semiconductor field effect transistor for improved electrical characteristics

The effect of wavelength of illumination on the trap occupancy of an optically biased GaN metal-semiconductor field effect transistor (MESFET) for its improved electrical characteristics is presented. The model evaluates the I d to V d characteristics and transconductance of the device for the cases of light turning both on and off at a reference time t = 0. The photovoltaic effect across the Schottky junction and the depletion width modulation in the active layer are taken into account along with the gate-length modulation and parasitic source and drain resistances. It is shown that the trap-related degradation of the drain characteristics could be overcome when the device is used under illumination with light acting as a dual gate.