Effect of diffraction and interference in submicron metal-semiconductor-metal photodetectors

As the dimensions of state-of-the art metal-semiconductor-metal photodetectors (MSMPD´s) decrease, effects that are insignificant for relatively large geometries become significant in the optoelectronic performance of submicron MSMPD´s. Accurate modeling of these effects Is necessary to precisely predict the performance of these devices by computer simulation. In this paper, a technique that accounts for the effect of diffraction from a single slot and interference from adjacent interelectrode gaps for front-illuminated MSMPD´s is presented. For the purpose of demonstrating the technique, InGaAs MSMPD´s illuminated with 1.55-μm wavelength have been simulated. The results are compared to the conventional shadowed exponential decay model. The new model predicts fundamentally different carrier distribution within the device. This disparity has been observed for devices with electrodes spaced up to 1.5 μm apart, emphasizing the significance of interference effects even for conventional devices