NEGF Modeling of Impact Ionization in Semiconductor Avalanche Photodiodes for Quantum Networking

TL;DR

This paper introduces a NEGF-based quantum transport simulation framework to model impact ionization in semiconductor avalanche photodiodes, crucial for advancing quantum networking technologies.

Contribution

It develops a non-perturbative, energy-resolved NEGF approach for impact ionization, capturing strongly inelastic scattering beyond semiclassical methods.

Findings

Demonstrates carrier multiplication emergence under high electric fields.

Analyzes energy-resolved transport and non-equilibrium charge distributions.

Provides a microscopic understanding of avalanche processes in nanoscale devices.

Abstract

We present an atomistic quantum transport simulation framework based on the Non-Equilibrium Green's Function (NEGF) formalism to model impact ionization in semiconductor avalanche devices, with direct relevance to near-term quantum networking applications. Conventional descriptions of avalanche breakdown rely predominantly on semiclassical simulation methods, such as local ionization coefficients, semiclassical carrier trajectories, or Monte Carlo sampling, all of which implicitly assume weak correlations and mean-field electronic interactions. These assumptions break down in nanoscale, high-field junctions where carrier multiplication emerges from strongly non-equilibrium, energy-resolved scattering processes. Our approach formulates impact ionization as a multi-particle self-energy within NEGF, enabling a non-perturbative, energy- and atomic orbital-resolved description of carrier multiplication directly from the device spectral function. This formulation captures strongly inelastic scattering processes beyond semiclassical approximations and is implemented in a matrix-based real-space representation suitable for nanoscale device modeling. Using a model semiconductor structure under high electric fields, we demonstrate the emergence of carrier multiplication and analyze its dependence on energy-resolved transport and nonequilibrium charge distributions. The framework provides insight into microscopic mechanisms governing avalanche processes and their impact on device performance. Our results establish a transport baseline for self-consistent calculations of the impact-ionization self-energy and carrier multiplication. By resolving the available and occupied states that underlie avalanche onset, this framework provides a route toward predictive modeling of silicon single-photon avalanche detectors and avalanche photodiodes used in quantum-network receivers.