Picosecond photoresponse in van der Waals heterostructures

TL;DR

This paper demonstrates that graphene/WSe2/graphene heterostructures achieve ultrafast picosecond photoresponse with high efficiency, revealing physical processes that enable rapid and effective photodetection in 2D material-based devices.

Contribution

It provides the first direct measurement of picosecond photoresponse in vdW heterostructures and insights into the physical mechanisms governing their speed and efficiency.

Findings

Photoresponse time as short as 5.5 ps

Tuning of response time via bias and layer thickness

Understanding of carrier drift and recombination processes

Abstract

Two-dimensional (2D) crystals, such as graphene and transition metal dichalcogenides (TMDs), present a collection of unique and complementary optoelectronic properties. Assembling different 2D materials in vertical heterostructures enables the combination of these properties in one device, thus creating multi-functional optoelectronic systems with superior performance. Here we demonstrate that graphene/WSe2/graphene heterostructures ally the high photodetection efficiency of TMDs with a picosecond photoresponse comparable to that of graphene, thereby optimizing both speed and efficiency in a single photodetector. We follow in time the extraction of photoexcited carriers in these devices using time-resolved photocurrent measurements and demonstrate a photoresponse time as short as 5.5 ps, which we tune by applying a bias and by varying the TMD layer thickness. Our study provides direct insight into the physical processes governing the detection speed and quantum efficiency of these van der Waals (vdW) heterostuctures, such as out-of-plane carrier drift and recombination. The observation and understanding of ultrafast and efficient photodetection demonstrate the potential of hybrid TMD-based heterostructures as a platform for future optoelectronic devices.