Contact-induced doping in aluminum-contacted molybdenum disulfide

TL;DR

This study investigates how aluminum contacts induce doping in MoS2 transistors, revealing that Al contacts facilitate tunneling-based carrier injection, leading to distinct electrical behaviors compared to traditional Ti/Au contacts.

Contribution

It demonstrates that aluminum contacts cause contact-induced doping in MoS2, primarily through tunneling mechanisms, which alters the device's electrical characteristics.

Findings

Al contacts reduce gate-voltage dependence of conductance.

Temperature dependence of conductance is smaller with Al contacts.

Carrier injection at Al contacts is dominated by tunneling, not thermally activated processes.

Abstract

The interface between two-dimensional semiconductors and metal contacts is an important topic of research of nanoelectronic devices based on two-dimensional semiconducting materials such as molybdenum disulfide (MoS2). We report transport properties of thin MoS2 flakes in a field-effect transistor geometry with Ti/Au and Al contacts. In contrast to widely used Ti/Au contacts, the conductance of flakes with Al contacts exhibits a smaller gate-voltage dependence, which is consistent with a substantial electron doping effect of the Al contacts. The temperature dependence of two-terminal conductance for the Al contacts is also considerably smaller than for the Ti/Au contacts, in which thermionic emission and thermally assisted tunneling play a dominant role. This result is explained in terms of the assumption that the carrier injection mechanism at an Al contact is dominated by tunneling that is not thermally activated.