MODELING OF WAVE-GUIDE PIN PHOTODETECTORS UNDER VERY HIGH OPTICAL POWER

In this paper, the behavior under very high optical power of waveguide PIN photodetectors grown on InP substrate is simulated. The problem i s solved using a pseudo-bidimensional Drift-Diffusion model which desc ribes the electrical behavior of the device including the effects of t he external circuit. The optical behavior of the device is analysed us ing FD 2D and 3D Beam Propagation Method. First, we present the optica l behavior of the device when the illumination conditions change. Infl uence of device structure, spot width, spot position and injection ang le on the quantum efficiency of the photodetector is so studied. Secon d, the whole modeling is validated using experimental results given in the literature. Three typical multimode structures which allow a high cut-off frequency as well as a good responsivity are then modeled and compared. The smaller one has a cut-off frequency of 75 GHz in small signal conditions and the main effect decreasing the microwave output signal when the optical input power increases is the carrier effect in the depletion region of the photodetector. The maximum microwave powe r of each photodetector is calculated in typical conditions of use.