The spatial extent of localized state wavefunctions in silicon inversion layers

Quantum Transport in Two-Dimensional WS2 with High-Efficiency Carrier Injection through Indium Alloy Contacts

Two-dimensional transition metal dichalcogenides (TMDCs) have properties attractive for optoelectronic and quantum applications. A crucial element for devices is the metal-semiconductor interface. However, high contact resistances have hindered progress. Quantum transport studies are scant as low-quality contacts are intractable at cryogenic temperatures. Here, temperature-dependent transfer length measurements are performed on chemical vapor deposition grown single-layer and bilayer WS₂ devices with indium alloy contacts. The devices exhibit low contact resistances and Schottky barrier heights (∼10 kΩ μm at 3 K and 1.7 meV). Efficient carrier injection enables high carrier mobilities (∼190 cm² V^-1 s^-1) and observation of resonant tunnelling. Density functional theory calculations provide insights into quantum transport and properties of the WS₂-indium interface. Our results reveal significant advances toward high-performance WS₂ devices using indium alloy contacts.

Nature of electronic states in atomically thin MoS₂ field-effect transistors

We present low-temperature electrical transport experiments in five field-effect transistor devices consisting of monolayer, bilayer, and trilayer MoS(2) films, mechanically exfoliated onto Si/SiO(2) substrate. Our experiments reveal that the electronic states in all films are localized well up to room temperature over the experimentally accessible range of gate voltage. This manifests in two-dimensional (2D) variable range hopping (VRH) at high temperatures, while below ∼30 K, the conductivity displays oscillatory structures in gate voltage arising from resonant tunneling at the localized sites. From the correlation energy (T(0)) of VRH and gate voltage dependence of conductivity, we suggest that Coulomb potential from trapped charges in the substrate is the dominant source of disorder in MoS(2) field-effect devices, which leads to carrier localization, as well.

The Anderson transition in silicon inversion layers: the origin of the random field and the effect of substrate bias

The purpose of this paper is to present results on and discuss the origin of Anderson localization in the inversion layer. Evidence is given for the existence of both negative and positive charges at the Si/SiO 2 interface. The negative charges contribute at least in part to the slow states at the Si/SiO 2 interface. The origin of these charges is discussed and a model proposed which provides an explanation of the conflicting reports on the value of minimum metallic conductivity, and the change in the extent of the localization as the distance between the carriers and the Si/SiO 2 interface is changed. It is suggested that in a two dimensional system long range potential fluctuations increase the minimum metallic conductivity above the value predicted, and found experimentally, for (the Anderson model with) short range potential fluctuations.