Tailoring the electroluminescence of dual-gated monolayer p–n diodes

Owing to their direct bandgaps and atomic-scale thickness, monolayer transition metal dichalcogenides have been heavily investigated for optoelectronic applications. Their potential for atomically-thin visible frequency light sources can be realized by lateral monolayer p–n diodes defined by local electrostatic gates. Control over the spectral distribution and polarization of the electroluminescence is desirable for integrating these prototypical monolayer LEDs into optoelectronic and nanophotonic devices with tunable coupling. The high electric fields near the p–n interface in these single-monolayer devices provide a route for in situ control of emission. Here, we discuss electrical tuning of the electroluminescence from the electrostatically-induced interface of gate-defined monolayer WSe₂ p–n diodes. We observe strong linear polarization (∼ 50%) of the electrically-pumped luminescence and a gate-tunable emission energy shift originating at this interface. Current-induced valley polarization, a possible avenue to achieving electrically-controlled circularly polarized emission, is also investigated with spatially-resolved Kerr rotation at cryogenic temperatures