Abstract
A two-dimensional numerical simulation based on the drift-diffusion model has been used to study the influence of the structural parameters on the ZnO-based thin film metal-semiconductor-metal photodiode's (MSM-PD) optical performance. A comparative study on photodiodes (PDs) with different structural parameters (active layer thickness, finger spacing, and width) at different illumination and biasing conditions has been conducted. The results of the simulation disclose the limit of using thicker active layer and wider finger spacing to achieve superior responsivity. In fact, the responsivity rapidly saturates, and a significant degradation in the response time befalls on the performance of the PD. The investigation suggests an optimum structure for the MSM-PD with about 0.2m active layer thickness, 5m finger spacing, and minimum achievable contact finger width.