Field-effect transistors and intrinsic mobility in ultra-thin MoSe2 layers

TL;DR

This paper demonstrates the fabrication of ultra-thin MoSe2 FETs with high gate modulation and investigates their intrinsic mobility and conductivity, revealing phonon scattering as a key factor affecting performance.

Contribution

It provides the first detailed measurement of intrinsic mobility and conductivity in ultra-thin MoSe2 FETs, highlighting the impact of Schottky barriers and phonon scattering.

Findings

High On/Off ratio (>10^6) in MoSe2 FETs

Asymmetric device characteristics due to Schottky barriers

Mobility strongly dependent on temperature, indicating phonon scattering

Abstract

We report the fabrication of back-gated field-effect transistors (FETs) using ultra-thin, mechanically exfoliated MoSe2 flakes. The MoSe2 FETs are n-type and possess a high gate modulation, with On/Off ratios larger than 106. The devices show asymmetric characteristics upon swapping the source and drain, a finding explained by the presence of Schottky barriers at the metal contact/MoSe2 interface. Using four-point, back-gated devices we measure the intrinsic conductivity and mobility of MoSe2 as a function of gate bias, and temperature. Samples with a room temperature mobility of ~50 cm2/V.s show a strong temperature dependence, suggesting phonons are a dominant scattering mechanism.