Screening limited switching performance of multilayer 2D semiconductor FETs: the case for SnS

Abstract

Gate tunable p-type multilayer tin mono-sulfide (SnS) field-effect transistor (FET) devices with SnS thickness between 50 and 100 nm were fabricated and studied to understand their performance. The devices showed anisotropic inplane conductance and room temperature field effect mobilities ∼5-10 cm V s. However, the devices showed an ON-OFF ratio ∼10 at room temperature due to appreciable OFF state conductance. The weak gate tuning behavior and finite OFF state conductance in the depletion regime of SnS devices are explained by the finite carrier screening length effect which causes the existence of a conductive surface layer from defect induced holes in SnS. Through etching and n-type surface doping by CsCO to reduce/compensate the not-gatable holes near the SnS flake's top surface, the devices exhibited an order of magnitude improvement in the ON-OFF ratio, and a hole Hall mobility of ∼100 cm V s at room temperature is observed. This work suggests that in order to obtain effective switching and low OFF state power consumption, two-dimensional (2D) semiconductor based depletion mode FETs should limit their thickness to within the Debye screening length of the carriers in the semiconductor.

Multi-Layer SnSe Nanoflake Field-Effect Transistors with Low-Resistance Au Ohmic Contacts

“…4c) in the p-SnSe nanoflake FET with Au metal contacts. A similar behavior was reported for other two-dimensional (2D) semiconducting materials with a similar thickness, including SnS FETs (thickness, ~50–80 nm) [43], ~15.8-nm-thick SnSe nanoplates [33], ~80-nm-thick MoS 2 [44], and ~84-nm-thick SnSe 2 [26]. These behaviors can be explained by the finite carrier screening length effect owing to the existence of a superficial conductive surface layer in FET devices with thicknesses larger than the screening length , where ε , K B , and p are the dielectric constant of the semiconductor, Boltzmann’s constant, and hole carrier density, respectively, [43].…”

Structural characterization of SnS crystals formed by chemical vapour deposition

“…However, this potential is currently unfulfilled, with record PCE of around 5% (Sinsermsuksakul et al, 2014), which is predominantly attributed to recombination at defects and grain boundaries. We are investigating SnS as a potential candidate for application as a p-type semiconductor in 2D Tunnel FETs and MOSFETs (Sucharitakul et al, 2016;Tian et al, 2017). SnS can take the form of several phases.…”

Multifield‐Inspired Tunable Carrier Effects Based on Ferroelectric‐Silicon PN Heterojunction

“…2020, 6,1900795 www.advancedsciencenews.com www.advelectronicmat.de simultaneous stimulation of electric and optical fields was designed. Electron.…”

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