Manipulating Picosecond Photoresponse in van der Waals Heterostructure Photodetectors

摘要

Self-powered ultrafast 2D photodetectors have demonstrated great potentialin imaging, sensing, and communication. Understanding the intrinsic ultrafastcharge carrier generation and separation processes is essential for achievinghigh-performance devices. However, probing and manipulating the ultrafastphotoresponse is limited either by the temporal resolution of the conventionalmethods or the required sophisticated device configurations. Here, van derWaals heterostructure photodetectors are constructed based on MoS_2/WSe_2p–n and n–n junctions and manipulate the picosecond photoresponse by combiningphotovoltaic (PV) and photothermoelectric (PTE) effects. Taking timeresolvedphotocurrent (TRPC) measurements, a TRPC peak at zero time delayis observed with decay time down to 4 ps in the n–n junction device, in contrastto the TRPC dip in the p–n junction and pure WSe_2 devices, indicating an oppositecurrent polarity between PV and PTE. More importantly, with an ultrafastphotocurrent modulation, a transition from a TRPC peak to a TRPC dip is realized,and detailed carrier transport dynamics are analyzed. This study providesa deeper understanding of the ultrafast photocurrent generation mechanism invan der Waals heterostructures and offers a new perspective in instruction fordesigning more efficient self-powered photodetectors.