Gate Dependent Electroluminescence of Interlayer Excitons in 2D Semiconductor Heterostructures

Monolayer transition metal dichalcogenides (TMDs) are two-dimensional (2D) semiconductors characterized by a direct band-gap and large exciton binding energies. Due to the 2D quantum confinement, their heterostructures exhibit a number of novel physical properties. By vertically stacking two different TMD monolayers, we can realize a type II heterostructure. In these heterostructures electrons and holes can be confined in individual layers, forming spatially separated long lived interlayer exciton (IE). In this work, we fabricate dual-gated MoSe₂/WSe₂ heterostructures encapsulated by boron nitride (BN) with electrical contacts in each layer. By applying forward bias voltage across the vertical junction, we observe gate tunable, near-infrared electroluminescence (EL) of interlayer excitons. By changing the relative doping between WSe₂ and MoSe₂ we can control the spatial location of EL emission. In addition, we find that EL lifetime is comparable to IE photoluminescence lifetime of ~300ns, showing that we can create long lived IE electrically. Such long lifetimes and spatial control pave the way to fully electrically addressable IE condensates, tunable near-IR excitonic lasers and other novel optoelectronic devices.