Generalized dc model of GaAs optical field effect transistor considering ion-implanted profile

Basic concepts and theory are developed for the effect of optical radiation on the do characteristics of a generalized model of an ion-implanted GaAs metal-semiconductor field effect transistor (MESFET). The optical radiation is allowed to fall on a transparent or semitransparent Schottky gate and the spacing between the gate source and gate drain. The continuity equations are solved for the excess carriers in the depletion region below the Schottky gate in the channel region and in the depletion region at the junction of the active layer and the substrate. The current-voltage (I-V) characteristics show a remarkable enhancement in the drain source current compared to opaque gate optically controlled field effect transistor (OPFET) (a special case of the generalized de model). This highlights the importance of two photovoltages developed across the Schottky junction and the channel-substrate junction. The transconductance, the channel conductance, and the photovoltages are also observed to be strongly affected by the flux densities. (C) 1998 Society of Photo-Optical Instrumentation Engineers.