Transit-time limited high-frequency response characteristics of MSM photodetectors

A simplified, but useful, one-dimensional transit-time limited frequency domain current response model of MSM photodetectors is presented. The model includes the effects of unequal velocities and lifetimes governing the lateral transport of photogenerated holes and electrons in the absorption layer. Normalized frequency response curves depicting the amplitude and phase versus the frequency are presented using the transit-time ratio as a parameter. The usefulness of the analytical response amplitude curves for the extraction of hole and electron transit times has been demonstrated by regressively fitting them with the measured results obtained from practical MSM photodetectors.