High speed optical detectors for monolithic millimeter wave integrated circuits

Metal-semiconductor-metal photodiodes with interdigitated Schottky barrier fingers are being developed for applications in monolithic optical receiver circuits with the purpose of detecting millimeter-wave modulation signals being transmitted via an optical carrier. The devices are planar and incorporate submicron finger spacings and a thin absorption region for speed with a buried stack of tuned Bragg reflectors for enhanced sensitivity at the carrier wavelength. These devices are being integrated with short-gate MODFET (modulation-doped field-effect transistor) amplifiers to form the complete monolithic integrated optical receiver circuit. Device measurements indicate a top surface reflectance of 0.5% with an operation bandwidth in excess of 40 GHz and a dynamic range of 33 dB.<>