Transient response of lateral photodetectors

A two-dimensional physical device model for characterizing the transient operation of lateral photodetectors is presented. It is based upon a corpuscular approach where the impulse response is constituted by the superposition of a large number of photocurrent pulses originating from spatially distributed discrete electron-hole pairs generated by an optical impulse. The motion of photogenerated carriers and the resulting photocurrent pulses in the external circuit are related by Ramo’s theorem which is shown to be fundamental for gaining a correct understanding of the time response of lateral detectors. The accuracy of the predictions obtained from the modeling is underpinned by their excellent agreement with experimental data on the impulse response of InP:Fe/InGaAs:Fe metal-semiconductor-metal detectors.