Sources of nonlinearity in a PIN photodetector at high applied reverse bias

One-dimensional (1D) and two-dimensional (2D) drift-diffusion models were created to investigate the sources of nonlinearity in a high-current p-i-n photodetector. Incomplete ionization, an external circuit, and impact ionization are all included in the model. We achieve good agreement with the experimental data with both the 1D and 2D model. We show that impact ionization is the dominant source of device nonlinearity at large applied reverse bias. The electron and hole current contributions to the second harmonic power were calculated. We find that the impact ionization is more important for the electrons. We also find that the hole velocity saturates slowly with increasing reverse bias, and the hole current makes a large contribution to the harmonic power at 10 V. This result implies that decreasing the hole injection will decrease the harmonic power.