Numerical analysis of the photoeffects in GaAs MESFET´s

The photoeffects on the I-V characteristics of GaAs MESFETs have been studied by a two-dimensional numerical method. It is theoretically verified that the photovoltaic effect occurring at the channel/substrate interface is responsible for the substantial increase of the drain current. The reverse gate current due to illumination is caused by sweep-out by the high electrical field in the gate depletion region, where a large gradient in the depth profile of the hole Fermi energy is found. For devices with a lightly doped n-type buffer layer, the increase of the drain current is less than for devices without a buffer layer, but is still substantial