Phonon-assisted Auger decay of excitons in doped transition metal dichalcogenide monolayers

TL;DR

This paper investigates how phonon-assisted Auger decay introduces a significant nonradiative pathway for excitons in doped TMDC monolayers, affecting their optical efficiency.

Contribution

It demonstrates that phonon-assisted Auger decay becomes prominent in TMDCs at low doping levels, providing a new understanding of exciton decay mechanisms.

Findings

Nonradiative lifetime ranges from 16 ps to 165 ps at low doping levels.

Phonon-assisted Auger decay competes with radiative decay in TMDC monolayers.

Decay rates depend on doping, temperature, and dielectric environment.

Abstract

The competition between the radiative and nonradiative lifetimes determines the optical quantum yield and plays a crucial role in the potential optoelectronic applications of transition metal dichalcogenides (TMDC). Here, we show that, in the presence of free carriers, an additional nonradiative decay channel opens for excitons in TMDC monolayers. Although the usual Auger decay channel is suppressed at low doping levels by the simultaneous momentum and energy conservation laws, exciton-phonon coupling relaxes this suppression. By solving a Bethe-Salpeter Equation, we calculate the phonon-assisted Auger decay rates in four typical TMDCs as a function of doping, temperature, and dielectric environment. We find that even for a relatively low doping of 10$^{12}$ cm$^{-2}$, the nonradiative lifetime ranges from 16 ps to 165 ps in different TMDCs, offering competition to the radiative decay channel.