Frequency and pulse response of a novel high-speed interdigital surface photoconductor (IDPC)

A novel type of high speed photodetector has been fabricated by placing an interdigital metal electrode pattern directly on the surface of a semi-insulating Cr-Doped GaAs substrate. The photo-conductor was found to have an analog bandwidth in excess of 4 GHz and a pulse risetime of less than 50 ps. Large photoconductive gain was observed under CW illumination. Photoconductive gain was less than unity under RF modulated illumination. The sensitivity, pulse and frequency response compare well with the best commercial detectors.