Modeling Sources of Nonlinearity in a Simple p-i-n Photodetector

Abstract

Abstract-Nonlinearity in p-i-n photodetectors leads to power generation at harmonics of the input frequency, limiting the performance of RF-photonic systems. We use one-dimensional and two-dimensional simulations of the drift-diffusion equations to determine the physical origin of the saturation in a simple heterojunction p-i-n photodetector at room temperature. Incomplete ionization, external loading, impact ionization, and the Franz-Keldysh effect are all included in the model. Impact ionization is the main source of nonlinearity at large reverse bias (>10 V in the device that we simulated). The electron and hole current contributions to the second harmonic power were calculated. We find that impact ionization has a greater effect on the electrons than it does on the holes. 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.Index Terms-2D simulation, impact ionization, nonlinearity, p-i-n photodetector.

Bandwidth Analysis of a p-π-n Si Photodetector

“…The results showed that the impact ionization has a greater effect on theelectrons than it does on the holes. The results also showed 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 [5]. The influencing parameters on the bandwidth are determined by the different mechanisms that transport the photo-generated charges to the contacts.…”

Simulation of a partially depleted absorber (PDA) photodetector

“…1 and 2, coupled with the heat flow equation. Compared with the p-i-n photodetector that was studied in [4], the temperature increases quickly in the PDA photodetector, because its electric field is higher than that in a p-i-n photodetector due to its thinner intrinsic layer. The output photocurrent in the experiment is also higher than in [4].…”

“…To study carrier transport in the photodetector, we model a PDA photodetector in two dimensions, longitudinal and radial, using the 2D drift-diffusion equations [2,4,[11][12][13] with the configuration of Figs. 1 and 2, coupled with the heat flow equation.…”

“…Nonlinearity in the photodetector leads to power generation at harmonics of the input signal frequencies, which limits the performance of these systems. We have studied the source of nonlinearity in a simple p-i-n photodetector [2][3][4], and we have found that impact ionization plays an important role in generating higher harmonic powers at high applied bias. We extend the model to study the sources of nonlinearity in a partially depleted absorber (PDA) photodetector [5], which has several absorption layers on each side of intrinsic region in PDA photodetector [5].…”

“…In this work, we use a 2D drift-diffusion model that uses one longitudinal and one radial dimension and assumes cylindrical symmetry. It has been shown in prior work that a 2D model produces more reliable results than a 1D purely longitudinal model, particularly at low reverse bias where transverse current flow is important [4]. It also allows us to avoid ad hoc assumptions for the radial intensity profile of the incident light.…”