Analysis of high speed interdigitated MSM photodetectors

The interdigitated MSM photodetector has a simple lateral structure with interdigitated metal finger electrodes deposited on a semiconductor substrate. This lateral structure gives rise to a very low capacitance and hence is capable of high speed operation. The structure is compatible with FET IC processes and so can be integrated easily into a receiver design. In this paper, the factors affecting the capacitance, responsivity and noise performance are reviewed. New formulas for the capacitance and the nonlinear variation of gain are given. A circuit model which takes into account both the electrode structure and the gain variation is also presented