Scaling and screening in long MSM photodiodes

MSM Photodetectors are strong candidates for use in high bit rate communicationsystems. Using conventional GaAs, bandwidths of up to 295 GHz have been measured [1]. It has been suggested that one way to improve the speed of these devices is to partially illuminate the photoconductive gap. The mechanism which gives rise to speed impovements is not fully understood [2]. The response has been found to be asymmetric with respect to the position of the focussed beam in the gap [3].