Electrically pumped WSe$_2$-based light-emitting van der Waals heterostructures embedded in monolithic dielectric microcavities

TL;DR

This paper demonstrates the integration of WSe2-based electroluminescent heterostructures into monolithic microcavities, significantly enhancing emission directionality and tunability, paving the way for compact vertical-cavity optoelectronic devices.

Contribution

It introduces a fully integrated WSe2 heterostructure within a dielectric microcavity, preserving optoelectronic properties and enabling control over emission characteristics.

Findings

Two bright cavity modes with high Q-factors observed in EL spectrum.

Emission intensity increases nearly 100-fold with microcavity embedding.

Peak emission wavelength tunable by over 35 nm via angle variation.

Abstract

Vertical stacking of atomically thin layered materials opens new possibilities for the fabrication of heterostructures with favorable optoelectronic properties. The combination of graphene, hexagonal boron nitride and semiconducting transition metal dichalcogenides allows fabrication of electroluminescence (EL) devices, compatible with a wide range of substrates. Here, we demonstrate a full integration of an electroluminescent van der Waals heterostructure in a monolithic optical microcavity made of two high reflectivity dielectric distributed Bragg reflectors (DBRs). Owing to the presence of graphene and hexagonal boron nitride protecting the WSe$_2$ during the top mirror deposition, we fully preserve the optoelectronic behaviour of the device. Two bright cavity modes appear in the EL spectrum featuring Q-factors of 250 and 580 respectively: the first is attributed directly to the monolayer area, while the second is ascribed to the portion of emission guided outside the WSe$_2$ island. By embedding the EL device inside the microcavity structure, a significant modification of the directionality of the emitted light is achieved, with the peak intensity increasing by nearly two orders of magnitude at the angle of the maximum emission compared with the same EL device without the top DBR. Furthermore, the coupling of the WSe$_2$ EL to the cavity mode with a dispersion allows a tuning of the peak emission wavelength exceeding 35 nm (80 meV) by varying the angle at which the EL is observed from the microcavity. This work provides a route for the development of compact vertical-cavity surface-emitting devices based on van der Waals heterostructures.