Fabrication, performance and modelling of high-speed GaAs MSM photodetectors

Short distance microwave and millimetre-wave fibre-optic links require high-speed photodetectors. Gallium Arsenide (GaAs) Metal-Semiconductor-Metal (MSM) photodetectors are not only capable of operating at frequencies of tens of GHz but also are intended for future planar integration with GaAs based Monolithic Microwave Integrated Circuits (MMICs). This paper presents results on MSM photodetectors of different geometries that were fabricated using optical lithography. They were tested and compared to an equivalent circuit to study the effect of device geometry on bandwidth and responsivity. The devices were measured to have a typical bandwidth of 9 GHz.