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.

中文翻译：

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使用嵌入式WSe2电荷池对WS2光电探测器进行选通。

2D光电检测器的性能通常由提供有效光选通效果的电荷陷阱控制。该器件具有超高的增益和响应度，但由于陷阱状态的寿命长，其代价是时间响应延迟。在这项工作中，我们设计了一种增益机制，该机制起源于II型2D横向异质结构中形成的大量电荷坑。使用嵌入了WSe2纳米点的石墨烯接触WS2光电探测器演示了此概念。在光照下，光激发载流子在WSe2 / WS2异质结（HJs）处被内置电场隔开，空穴被困在WSe2纳米点中。最终的WSe2空穴水坑提供了光电导增益，因为电子在保留在水坑中的空穴寿命期间不断循环。WSe2 / WS2 HJ光电探测器的响应度为3×102 A / W，每个光子的增益为7×102电子。同时，归因于WSe2 / WS2 HJ中超快的层内激子动力学，与石墨烯接触的原始WS2单层和WS2 / MoS2异质双层光电探测器的先前报告相比，零门响应时间减少了5个数量级。