numerical modeling of the temporal response of back-gated metalsemiconductor- metal photodetector in an equilibrium condition

we have simulated the carrier concentration and temporal response characteristics of a back-gated metal- semiconductor-metal (bg-msm) photodetector in one dimension as a function of optical pulse position on the active region in an equilibrium condition (without bias voltage to the photodetector). we have adopted a nonlinear ambipolar transport model to simulate the behavior of photo-generated carriers in the active region of the bg-msm photodetector. from the simulation results, it is observed that for optical pulse positions in the cathode region, the magnitude of the response current is exactly the same but opposite that of the anode region. the response of the photodetector is zero when a pulse is positioned at the center of the active region. this important feature of the device could make it attractive for micro-scale positioning of highly sensitive instruments. our simulation results agreed well with the experimental results.