Analytical Model of Cutoff Frequency of GaAs PIN Photodiode

Abstract

This work has developed an analytical model of the cutoff frequency for a GaAs p-i-n photodiode, which can be employed to investigate the high-frequency response– a key concern for the applications of high-speed optical communications. In doing so, the three transit times for the highly and uniformly doped emitter and base regions and the intrinsic region sandwiched between these regions have been determined, which requires the solutions of governing differential equations for each region. The analytical model considers the effects of the surface and volume recombination on the emitter and base regions. The electric field in the intrinsic layer is assumed to be constant, whereas the emitter and base regions are considered zero. The calculated transit time (10-15 ps) and the cutoff frequency (≈ 10 GHz) obtained through the simulations of the developed model in MATLAB environment show the same order of magnitudes observed in a practical p-i-n photodiode. The model results also show that the cutoff frequency strongly depends on the width of the intrinsic layer and the applied reverse bias voltage.