Journal
ACS NANO
Volume 14, Issue 4, Pages 4559-4566Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.0c00098
Keywords
WS2; TMD; 2D material; photodetector; heterostructure; photogating
Categories
Funding
- Ministry of Science and Technology of Taiwan [MOST 107-2119-M007-011-MY2, MOST 106-2119-M-007-008-MY3, MOST 106-2628-M-007-003-MY3, MOST 108-2112-M-006-010]
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Performance of 2D photodetectors is often predominated by charge traps that offer an effective photogating effect. The device features an ultrahigh gain and responsivity, but at the cost of a retarded temporal response due to the nature of long-lived trap states. In this work, we devise a gain mechanism that originates from massive charge puddles formed in the type-II 2D lateral heterostructures. This concept is demonstrated using graphene-contacted WS2 photodetectors embedded with WSe2 nanodots. Upon light illumination, photoexcited carriers are separated by the built-in field at the WSe2/WS2 heterojunctions (HJs), with holes trapped in the WSe2 nanodots. The resulting WSe2 hole puddles provide a photoconductive gain, as electrons are recirculating during the lifetime of holes that remain trapped in the puddles. The WSe2/WS2 HJ photodetectors exhibit a responsivity of 3 X 10(2) A/W with a gain of 7 X 10(2) electrons per photon. Meanwhile, the zero-gate response time is reduced by 5 orders of magnitude as compared to the prior reports for the graphene-contacted pristine WS2 monolayer and WS2/MoS2 heterobilayer photodetectors due to the ultrafast intralayer excitonic dynamics in the WSe2/WS2 HJs.
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