Electric field induced strong enhancement of electroluminescence in multi-Layer MoS2

TL;DR

This paper demonstrates that applying an electric field significantly enhances electroluminescence in multi-layer MoS2 and other TMDs, surpassing monolayer efficiencies and enabling new optoelectronic device possibilities.

Contribution

It reveals that electric fields induce strong electroluminescence in multi-layer TMDs, with efficiencies comparable or superior to monolayers, due to carrier redistribution from indirect to direct bandgap states.

Findings

Electroluminescence efficiency in multi-layer MoS2 exceeds that of monolayers.

Electric field causes carrier redistribution from indirect to direct bandgap states.

Enhanced electroluminescence observed in WSe2 and other TMDs.

Abstract

The layered transition metal dichalcogenides (TMDs) have attracted considerable interest due to their unique electronic and optical properties. Here we report electric field induced strong electroluminescence in multi-layer MoS2 and WSe2. We show that GaN-Al2O3-MoS2 and GaN-Al2O3-MoS2-Al2O3-graphene vertical heterojunctions can be created with excellent rectification behaviour. Electroluminescence studies demonstrate prominent direct bandgap excitonic emission in multi-layer MoS2 over the entire vertical junction area. Importantly, the electroluminescence efficiency observed in multi-layer MoS2 is comparable to or even higher than that in monolayers, corresponding to a relative electroluminescence enhancement factor of >1000 in multi-layer MoS2 when compared to its photoluminescence. This striking enhancement of electroluminescence can be attributed to the high electric field induced carrier redistribution from low energy points (indirect bandgap) to high energy points (direct bandgap) of k-space, arising from the unique band structure of MoS2 with a much higher density of states at high energy points. The electric field induced electroluminescence is general for other TMDs including WSe2, and can provide a fundamental platform to probe the carrier injection, population and recombination in multi-layer TMDs and open up a new pathway toward TMD based optoelectronic devices.