Quasi-two-dimensional simulation of an ion-implanted GaAs MESFET photodetector

A quasi-two-dimensional numerical model of an optically gated GaAs metal se miconductor field-effect transistor (MESFET) has been developed for the cha racterization of the device as a photodetector The model considers the chan nel to be nonuniformly doped. The model involves the solution of a 1-D Pois son's equation, and takes into account the field-dependent mobility of the carriers in the channel for computation Of the current. It has been found t hat, in a short-channel MESFET photodetector, the drain current saturation is caused by the velocity saturation of the carriers rather than pinch off. The photocurrent gain, responsivity, and the input RC time constant of an ion-implanted GaAs MESFET having a semitransparent metal gate have been est imated rent gain. a high responsibility, and a low-input RC time constant a t an operating wavelength of 0.85 mu m. (C) 2000 John Wiley & Sons, Inc.