LIGHT-INDUCED SIDEGATING EFFECT IN GAAS-MESFETS

Abstract

Light sensitivity of sidegating effect in GaAs MESFET's is investigated by performing two-dimensional numerical simulations on realistic sidegate structures. Mechanism of the light-induced sidegating is identified and compared with alternative mechanisms of sidegating including trap-fill-limited conduction and conduction through the Schottky-i-n(sidegate) structure. Ionization of hole traps in the substrate by capturing the photo-generated holes is found to be the major cause of light-induced sidegating effect which occurs even at very low sidegate voltages. In the presence of the hole traps occupied by holes, the potential distribution in the electron-trap-rich substrate becomes similar to that in the hole-trap-rich substrate, i.e., the negative voltage applied to the sidegate is carried over to the channel-substrate interface.