Scanning photocurrent microscopy reveals electron-hole asymmetry in ionic liquid-gated WS2 transistors

Abstract

We perform scanning photocurrent microscopy on WS2 ionic liquid-gated field effect transistors exhibiting high-quality ambipolar transport. By properly biasing the gate electrode we can invert the sign of the photocurrent showing that the minority photocarriers are either electrons or holes. Both in the electron- and the hole-doping regimes the photocurrent decays exponentially as a function of the distance between the illumination spot and the nearest contact, in agreement with a two-terminal Schottky-barrier device model. This allows us to compare the value and the doping dependence of the diffusion length of the minority electrons and holes on a same sample. Interestingly, the diffusion length of the minority carriers is several times larger in the hole accumulation regime than in the electron accumulation regime, pointing out an electron-hole asymmetry in WS2.

References in corpus (12)

• Atomically thin MoS2: A new direct-gap semiconductor
• Evolution of Electronic Structure in Atomically Thin Sheets of WS2 and WSe2
• How does quantum confinement influence the electronic structure of transition metal sulfides TmS2
• Extraordinary room-temperature photoluminescence in WS2 monolayers
• Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides
• Large and tunable photo-thermoelectric effect in single-layer MoS2
• Photo-Thermoelectric Effect at a Graphene Interface Junction
• Novel High-Mobility Field-Effect Transistors Based on Transition Metal Dichalcogenides
• Photocurrent imaging and efficient photon detection in a graphene transistor
• Quantitative Determination of the Band-Gap of WS2 with Ambipolar Ionic Liquid-Gated Transistors
• Transistors with Chemically Synthesized Layered Semiconductor WS2 Exhibiting 105 Room Temperature Modulation and Ambipolar Behavior
• Elucidating the photoresponse of ultrathin MoS2 field-effect transistors by scanning photocurrent microscopy

Cited by in corpus (8)

• Electrostatically Induced Superconductivity at the Surface of WS${}_2$
• Fast and Highly Sensitive Ionic Polymer Gated WS${}_2$-Graphene Photodetectors
• Quasi 1D electronic transport in a 2D magnetic semiconductor
• Manipulating Spin-polarized Photocurrent in 2D Transition Metal Dichalcogenides
• Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength Dependent Mapping
• Enhanced electron-phonon interaction in multi-valley materials
• Ionic Gate Spectroscopy of 2D Semiconductors
• Light matter interaction in WS${}_2$ nanotube-graphene hybrid devices