Sub 20 meV Schottky barriers in metal/MoTe ₂ junctions

Abstract

The newly emerging class of atomically-thin materials has shown a high potential for the realisation of novel electronic and optoelectronic components. Amongst this family, semiconducting transition metal dichalcogenides (TMDCs) are of particular interest. While their band gaps are compatible with those of conventional solid state devices, they present a wide range of exciting new properties that is bound to become a crucial ingredient in the future of electronics. To utilise these properties for the prospect of electronics in general, and long-wavelength-based photodetectors in particular, the Schottky barriers formed upon contact with a metal and the contact resistance that arises at these interfaces have to be measured and controlled. We present experimental evidence for the formation of Schottky barriers as low as 10 meV between MoTe 2 and metal electrodes. By varying the electrode work functions, we demonstrate that Fermi level pinning due to metal induced gap states at the interfaces occurs at 0.14 eV above the valence band maximum. In this configuration, thermionic emission is observed for the first time at temperatures between 40 K and 75 K. Finally, we discuss the ability to tune the barrier height using a gate electrode.

Charge Density Depinning in Defective MoTe2 Transistor by Oxygen Intercalation

“…For instance, unipolar n ‐type, p ‐type, as well as ambipolar characteristics were measured in the MoTe 2 FETs, which are irrelevant to the work functions of the contact metals. [ 8–12 ] Furthermore, a study reported a weak Fermi level pinning at the metal–MoTe 2 interface, [ 13 ] whereas others argued a strong pinning with a factor as small as 0.07. [ 14 ] These inconsistencies are not well understood and set obstacles to the practical applications of this material in electronics.…”

Tuning the Polarity of MoTe2 FETs by Varying the Channel Thickness for Gas-Sensing Applications

“…In addition to the possible effect of reduced MoTe 2 channel thickness on n-type doping efficiency, we also speculate that the polarity switching from n- to p-type in thinner layers may be caused by the modulation of Schottky barrier height (SBH) and corresponding band alignment and band-bending at the metal/MoTe 2 interface. The effective barrier height for Ti, Cr, and Pd contacts are 41.1, 40.3, and 10.2 meV, respectively [41,42].…”

Energy dispersive spectroscopic measurement of charge traps in MoTe2

“…A 2 is also affected by the effective mobility of the charge carriers. As V g2 approaches the subthreshold region of the transfer curve, the current transport becomes limited by thermionic emission over the Schottky barrier [30], thus changing A 2 . The changes in the device conductivity can be modeled, to a first approximation, as a linear perturbation in the mobility δμ, so μ a = μ b + δμ.…”