Exciton-related electroluminescence from monolayer MoS2

TL;DR

This study investigates the microscopic origins of electroluminescence in monolayer MoS2, revealing exciton recombination processes and Auger effects, and introduces electrical injection as a tool to control excitonic phenomena.

Contribution

It provides new insights into exciton recombination mechanisms in MoS2 using electrical injection, enabling better control of valley and spin excitations in 2D materials.

Findings

Identification of direct and bound exciton recombination processes.

Observation of Auger recombination at high injection rates.

Absence of direct exciton saturation indicating long exciton lifetimes.

Abstract

Excitons in MoS2 dominate the absorption and emission properties of the two-dimensional system. Here, we study the microscopic origin of the electroluminescence from monolayer MoS2 fabricated on a heavily p-type doped silicon substrate. By comparing the photoluminescence and electroluminescence of a MoS2 diode, direct-exciton and bound-exciton related recombination processes can be identified. Auger recombination of the exciton-exciton annihilation of bound exciton emission is observed under a high electron-hole pair injection rate at room temperature. We expect the direct exciton-exciton annihilation lifetime to exceed the carrier lifetime, due to the absence of any noticeable direct exciton saturation. We believe that our method of electrical injection opens a new route to understand the microscopic nature of the exciton recombination and facilitate the control of valley and spin excitation in MoS2.