Tunable Emission from Localized Excitons Deterministically Positioned in Monolayer <i>p</i>–<i>n</i> Junctions

Abstract

Transition metal dichalcogenides (TMDs) are a promising solid-state platform for single photon emission. The versatile fabrication methods afforded by their two-dimensional nature facilitate the integration of TMDs into optoelectronic devices where localized exciton states can be electrically pumped. While this functionality is highly desirable for applications in quantum nanophotonics, enabling more compact and scalable devices, the lack of control of emitter spatial positions and energies has impeded the integration of TMDs into quantum optical systems. Here we demonstrate single photon electroluminescence from monolayer WSe2 in a lateral gate-defined junction that allows the electrostatic environment to be tuned in situ. By utilizing local strain engineering, we reliably position bright localized exciton states in the optically active region of the gate-defined junction, enabling the deterministic creation of devices that predominantly produce single photon emission. Modulation of the gate voltages tunes the emission between different electrostatic regimes, revealing a new localized exciton state that exhibits a gate-dependent red-shift. A spectral shift of the electroluminescence of over 10 meV is achieved, demonstrating the capability for simultaneous electrical pumping and tuning of localized exciton emission in TMD devices.