title: Interlayer Exciton Optoelectronics in a 2D Heterostructure p-n Junction.
abstract: Semiconductor heterostructures are backbones for solid-state-based optoelectronic devices. Recent advances in assembly techniques for van der Waals heterostructures have enabled the band engineering of semiconductor heterojunctions for atomically thin optoelectronic devices. In two-dimensional heterostructures with type II band alignment, interlayer excitons, where Coulomb bound electrons and holes are confined to opposite layers, have shown promising properties for novel excitonic devices, including a large binding energy, micron-scale in-plane drift-diffusion, and a long population and valley polarization lifetime. Here, we demonstrate interlayer exciton optoelectronics based on electrostatically defined lateral p-n junctions in a MoSe2-WSe2heterobilayer. Applying a forward bias enables the first observation of electroluminescence from interlayer excitons. At zero bias, the p-n junction functions as a highly sensitive photodetector, where the wavelength-dependent photocurrent measurement allows the direct observation of resonant optical excitation of the interlayer exciton. The resulting photocurrent amplitude from the interlayer exciton is about 200 times smaller than the resonant excitation of intralayer exciton. This implies that the interlayer exciton oscillator strength is 2 orders of magnitude smaller than that of the intralayer exciton due to the spatial separation of electron and hole to the opposite layers. These results lay the foundation for exploiting the interlayer exciton in future 2D heterostructure optoelectronic devices.
authors.forename: Jason S
authors.initials: JS
authors.lastname: Ross
authors.forename: Pasqual
authors.identifier: 0000-0002-5909-1686
authors.initials: P
authors.lastname: Rivera
authors.forename: John
authors.initials: J
authors.lastname: Schaibley
authors.forename: Eric
authors.initials: E
authors.lastname: Lee-Wong
authors.affiliation: Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong , Hong Kong, China.
authors.forename: Hongyi
authors.initials: H
authors.lastname: Yu
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science , Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science , Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Kenji
authors.identifier: 0000-0003-3701-8119
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Jiaqiang
authors.initials: J
authors.lastname: Yan
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: David
authors.initials: D
authors.lastname: Mandrus
authors.forename: David
authors.initials: D
authors.lastname: Cobden
authors.affiliation: Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong , Hong Kong, China.
authors.forename: Wang
authors.initials: W
authors.lastname: Yao
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Xu
keywords: interlayer exciton; optoelectronics; p−n junction; transition metal dichalcogenides; van der Waals heterostructure