Fast and Highly Sensitive Ionic Polymer Gated WS${}_2$-Graphene Photodetectors

Abstract

The combination of graphene with semiconductor materials in heterostructure photodetectors, has enabled amplified detection of femtowatt light signals using micron-scale electronic devices. Presently, the speed of such detectors is limited by long-lived charge traps and impractical strategies, e.g. the use of large gate voltage pulses, have been employed to achieve bandwidths suitable for applications, such as video-frame-rate imaging. Here, we report atomically thin graphene-WS${}_2$ heterostructure photodetectors encapsulated in an ionic polymer, which are uniquely able to operate at bandwidths up to 1.5 kHz, whilst maintaining internal gain as large as $10^6$. Highly mobile ions and a nanometre scale Debye length of the ionic polymer are used to screen charge traps and tune the Fermi level of graphene over an unprecedented range at the interface with WS${}_2$. We observe a responsivity $R=10^6$ A W${}^{-1}$ and detectivity $D^{\ast }=3.8\times 10^{11}$ Jones, approaching that of single photon counters. The combination of both high responsivity and fast response times makes these photodetectors suitable for video-frame-rate imaging applications.

10 pages, 4 figures. To appear in Advanced Materials

References in corpus (6)

• Graphene photodetectors for high-speed optical communications
• Electrical Transport Properties of Single-Layer WS2
• Probing excitonic states in ultraclean suspended two-dimensional semiconductors by photocurrent spectroscopy
• Measurement of high exciton binding energy in the monolayer transition-metal dichalcogenides WS2 and WSe2
• High quality monolayer graphene synthesized by resistive heating cold wall chemical vapour deposition
• Scanning photocurrent microscopy reveals electron-hole asymmetry in ionic liquid-gated WS2 transistors

Cited by in corpus (10)

• Long-Lived Charge Separation Following Pump-Energy Dependent Ultrafast Charge Transfer in Graphene/WS${}_2$ Heterostructures
• Structure, preparation, and applications of 2D material-based metal-semiconductor heterostructures
• Superlubricity of epitaxial monolayer WS2 on graphene
• Highly efficient rubrene-graphene charge transfer interfaces as phototransistors in the visible regime
• Graphene-based light sensing: fabrication, characterisation, physical properties and performance
• Alternating superconducting and charge density wave monolayers within bulk 6R-TaS2
• Strain-engineering of twist-angle in graphene/hBN superlattice devices
• Asymmetrically Encapsulated vertical ITO/MoS2/Cu2O photodetector with ultra-high sensitivity
• Ultrahigh Responsivity Photodetectors of Two-dimensional Covalent Organic Frameworks Integrated on Graphene
• High Responsivity Gate Tunable UV-Visible Broadband Phototransistor Based on Graphene-WS2 Mixed Dimensional (2D-0D) Heterostructure