Impact of band-anticrossing on band-to-band tunneling in highly-mismatched semiconductor alloys

TL;DR

This paper investigates how band-anticrossing effects in highly-mismatched semiconductor alloys influence band-to-band tunneling, revealing deviations from traditional models and implications for electronic device performance.

Contribution

It provides a theoretical analysis of BTBT in dilute nitride and bismide alloys, highlighting the impact of band-anticrossing interactions on tunneling behavior beyond Kane model assumptions.

Findings

BAC reduces BTBT at low electric fields

BAC increases BTBT at high electric fields

Field-dependent competition affects tunneling mechanisms

Abstract

We theoretically analyse band-to-band tunneling (BTBT) in highly-mismatched, narrow-gap dilute nitride and bismide alloys, and quantify the impact of the N- or Bi-induced perturbation of the band structure -- due to band-anticrossing (BAC) with localised impurity states -- on the electric field-dependent BTBT generation rate. For this class of semiconductors the assumptions underpinning the widely-employed Kane model of direct BTBT break down, due to the strong band edge nonparabolicity resulting from BAC interactions. Via numerical calculations based on the Wentzel-Kramers-Brillouin approximation we demonstrate that BAC leads, at fixed band gap, to reduced (increased) BTBT current at low (high) applied electric fields compared to that in a conventional InAs$_{1-x}$Sb$_{x}$ alloy. Our analysis reveals that BTBT in InN$_{x}$As$_{1-x}$ and InAs$_{1-x}$Bi$_{x}$ is governed by a field-dependent competition between the impact of N (Bi) incorporation on (i) the dispersion of the complex band linking the valence and conduction bands, which dominates at low field strengths, and (ii) the conduction (valence) band edge density of states, which dominates at high field strengths. The implications of our results for applications in avalanche photodiodes and tunneling field-effect transistors are discussed.