# Carrier recombination mechanism at defects in wide band gap two-dimensional materials from first principles

## TL;DR

This study develops first-principles methods to understand carrier recombination at defects in 2D materials, revealing defect-defect state dominance and the influence of strain on non-radiative rates, aiding quantum emitter design.

## Contribution

It introduces a first-principles framework for analyzing recombination mechanisms at defects in 2D materials, highlighting defect-defect state dominance and strain effects.

## Key findings

- Carrier recombination in 2D is dominated by defect-defect state processes.
- Strain significantly alters electron-phonon coupling and non-radiative rates.
- The methods provide insights for engineering quantum efficiency in 2D SPEs.

## Abstract

Identification and design of defects in two-dimensional (2D) materials as promising single photon emitters (SPE) requires a deep understanding of underlying carrier recombination mechanisms. Yet, the dominant mechanism of carrier recombination at defects in 2D materials has not been well understood, and some outstanding questions remain: How do recombination processes at defects differ between 2D and 3D systems? What factors determine defects in 2D materials as excellent SPE at room temperature? In order to address these questions, we developed first-principles methods to accurately calculate the radiative and non-radiative recombination rates at defects in 2D materials, using h-BN as a prototypical example. We reveal the carrier recombination mechanism at defects in 2D materials being mostly dominated by defect-defect state recombination in contrast to defect-bulk state recombination in most 3D semiconductors. In particular, we disentangle the non-radiative recombination mechanism into key physical quantities: zero-phonon line (ZPL) and Huang-Rhys factor. At the end, we identified strain can effectively tune the electron-phonon coupling at defect centers and drastically change non-radiative recombination rates. Our theoretical development serves as a general platform for understanding carrier recombination at defects in 2D materials, while providing pathways for engineering of quantum efficiency of SPE.