Photogating WS₂ Photodetectors Using Embedded WSe₂ Charge Puddles

Abstract

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 × 102 A/W with a gain of 7 × 102 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.

The Photodetectors Based on Lateral Monolayer MoS2/WS2 Heterojunctions

“…Particularly, high responsivity of 567.6 A/W and detectivity of ~ 10 11 Jones are achieved for the photodetectors attributing to the photogating effect. The performance of the proposed lateral MoS 2 /WS 2 heterojunction photodetectors is better than or comparable to the reported work [ 24 , 62 , 76 , 78 , 86 , 97 , 98 ]. In addition, we suppose the undesired 1/f noise arising from the trapping/detrapping of charge carriers maybe further reduced by high-quality and defect-less channel material.…”

A review of molybdenum disulfide (MoS2) based photodetectors: from ultra-broadband, self-powered to flexible devices

“…[133][134][135] Furthermore, the high carrier mobility and strong interaction of TMDs with light make these 2D materials interesting for optoelectronic applications. Atomically thin layered TMDs, including MoS 2 , [136][137][138][139][140] MoSe 2 , [141][142][143][144] MoTe 2 , 145,146 WS 2 , 147,148 WSe 2 /WS 2 , 149 WSe 2 , 120,150 WSe 2 /h-BN, 151 HfS 2 , 152,153 ReS 2 , 154,155 ReSe 2 , 156,157 SnS 2 , 158,159 and WSe 2 /SnSe 2 , 160 and the doped MoS 2 heterostructures 161 have been studied for use in broadband photodetectors. Among 2D TMDs, MoS 2 atomic layers have also been extensively investigated for developing MoS 2 hybrid heterostructure-based photodetectors in combination with other materials, including MoS 2 /Si, 162 AuNPs/ MoS 2 , 163 MoS 2 /WS 2 , 164 MoS 2 /WSe 2 , 165 graphene/MoS 2 /WSe 2 /graphene, 165 MoTe 2 /MoS 2 , 166 GaTe/MoS 2 , 167 PdSe 2 /MoS 2 , 168 MoS 2 / graphene, 169 and MoS 2 /BP.…”

Embedment of Multiple Transition Metal Impurities into WS2 Monolayer for Bandstructure Modulation

“…This retains the semiconducting properties for their applications in electronic and optoelectronic devices. [ 10,21,22 ] This weak electron doping is also reflected in the presence of a small charged exciton peak at 1.98 eV. In the PL response of MED WS 2 , the most prominent feature lies in a broad peak, centered near 1.86 eV.…”