3 years ago

Tunneling Photocurrent Assisted by Interlayer Excitons in Staggered van der Waals Hetero-Bilayers

Tunneling Photocurrent Assisted by Interlayer Excitons in Staggered van der Waals Hetero-Bilayers
Quoc An Vu, Ganesh Ghimire, Jin Hee Lee, Shrawan Roy, Dinh Hoa Luong, Guru Prakash Neupane, Hyun Seok Lee, Young Hee Lee
Vertically stacked van der Waals (vdW) heterostructures have been suggested as a robust platform for studying interfacial phenomena and related electric/optoelectronic devices. While the interlayer Coulomb interaction mediated by the vdW coupling has been extensively studied for carrier recombination processes in a diode transport, its correlation with the interlayer tunneling transport has not been elucidated. Here, a contrast is reported between tunneling and drift photocurrents tailored by the interlayer coupling strength in MoSe2/MoS2 hetero-bilayers (HBs). The interfacial coupling modulated by thermal annealing is identified by the interlayer phonon coupling in Raman spectra and the emerging interlayer exciton peak in photoluminescence spectra. In strongly coupled HBs, positive photocurrents are observed owing to the inelastic band-to-band tunneling assisted by interlayer excitons that prevail over exciton recombinations. By contrast, weakly coupled HBs exhibit a negative photovoltaic diode behavior, manifested as a drift current without interlayer excitonic emissions. This study sheds light on tailoring the tunneling transport for numerous optoelectronic HB devices. A contrast between tunneling and drift photocurrents tailored by the interlayer coupling strength is reported in MoSe2/MoS2 hetero-bilayers. In strongly coupled hetero-bilayers modulated by thermal annealing, a positive photocurrent is observed owing to inelastic band-to-band tunneling assisted by interlayer excitons. In contrast, weakly coupled hetero-bilayers exhibit a negative photovoltaic diode behavior, manifested as a drift current without interlayer excitonic emissions.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/adma.201701512

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