Polarity Tunable Trionic Electroluminescence in Monolayer WSe2

• Published in: Nano letters Vol. 19; no. 10; pp. 7470 - 7475
• Main Authors: Wang, Junyong, Lin, Fanrong, Verzhbitskiy, Ivan, Watanabe, Kenji, Taniguchi, Takashi, Martin, Jens, Eda, Goki
• Format: Journal Article
• Language: English
• Published: American Chemical Society 09-10-2019
• Subjects: trion; Transition metal dichalcogenides; electroluminescence; field-emission tunneling
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.9b03215

Monolayer WSe2 exhibits luminescence arising from various types of exciton complexes due to strong many-body effects. Here, we demonstrate selective electrical excitation of positive and negative trions in van der Waals metal–insulator–semiconductor (MIS) heterostructure consisting of few-layer graphene (FLG), hexagonal boron nitride (hBN), and monolayer WSe2. Intentional unbalanced injection of electrons and holes is achieved via field-emission tunneling and electrostatic accumulation. The device exhibits planar electroluminescence from either positive trion X+ or negative trion X– depending on the bias conditions. We show that hBN serves as a tunneling barrier material allowing selective injection of electron or holes into WSe2 from FLG layer. Our observation offers prospects for hot carrier injection, trion manipulation, and on-chip excitonic devices based on two-dimensional semiconductors.