Full-Band Monte Carlo Simulation of HgCdTe APDs

Abstract

A full-band Monte Carlo model has been developed for understanding the carrier multiplication process in HgCdTe infrared avalanche photodiodes. The proposed model is based on a realistic electronic structure obtained by pseudopotential calculations and a phonon dispersion relation determined by ab initio techniques. The calculated carrier-phonon scattering rates are consistent with the electronic structure and the phonon dispersion relation, thus removing adjustable parameters such as deformation potential coefficients. The computation of the impact ionization transition rate is based on the calculated electronic structure and the corresponding wavevector-dependent dielectric function. The Monte Carlo model is applied to investigate key performance figures of long-wavelength infrared (LWIR) and mid-wavelength infrared (MWIR) HgCdTe avalanche photodetectors such as carrier multiplication and noise properties. Good agreement is achieved between simulations and experimental results. The multiplication process in LWIR (k c = 9.0 lm at 80 K) and MWIR (k c = 5.1 lm at 80 K) devices is found to be initiated only by electrons, as expected from excess noise measurements. This single-carrier multiplication behavior can be traced back to the details of the computed valence-band structure and phonon scattering rates.

A 2D Full-Band Monte Carlo Study of HgCdTe-Based Avalanche Photodiodes

“…[29][30][31][32][33] In Ref. 3 we reported the results of a one-dimensional Monte Carlo analysis performed on the device structure grown by Derelle et al 9 We have shown that our model satisfactorily reproduces the measured gain and noise characteristics of this device. Although one-dimensional (1D) models are useful to understand the physics of these kinds of devices, they cannot capture the more complex carrier dynamics that takes place in realistic 2D and three-dimensional (3D) structures; for example, it is not possible to evaluate the position-dependent gain or to study edge effects.…”

“…HgCdTe-based avalanche photodetectors (APD) provide the best performance as they are characterized by high sensitivity and gain while exhibiting very low multiplication noise. [1][2][3] These features are intimately related to the material properties of HgCdTe alloys with cadmium concentrations below 53%. In fact, for these alloys, the impact ionization process is due almost exclusively to electrons, while holes do not contribute.…”

“…Wang presented an expression for the electron impact ionization rate under moderate electric fields within the framework of the Lei-Ting balance equation approach. 14 Recently, Bertazzi et al 3 performed a comprehensive study of the impact ionization process in MWIR and LWIR HgCdTe based on a full-band Monte Carlo (FBMC) model. The present work aims at investigating the performance of HgCdTe diffused APDs using a twodimensional (2D) FBMC.…”

“…The manuscript is organized as follows: Section ''Numerical Model'' presents a brief description of the FBMC model presented in Ref. 3. Section ''Results'' outlines the 2D aspects of the numerical model and describes the results obtained.…”

Simulation of infrared avalanche photodiodes from first principles

“…It is of interest to observe how the alloy scattering rate compares for two other band models used recently 6,22 . Table 2 shows the electron alloy scattering rates at four electron energies referenced to the conduction band edge.…”