Modeling of a Vertical Tunneling Transistor Based on Graphene–MoS2Heterostructure

Abstract

In this paper, for the first time, we present a computational study on the electrical behavior of the field-effect tunneling transistor based on vertical graphene–MoS2 heterostructure and vertical graphene nanoribbon–MoS2 heterostructure. Our simulation is based on nonequilibrium Green’s function formalism along with an atomistic tight-binding (TB) model. The TB parameters are obtained by fitting the bandstructure to first-principle results. By using this model, electrical characteristics of device, such as ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratio, subthreshold swing, and intrinsic gate-delay time, are investigated. We show that the combination of tunneling and thermionic transport allows modulation of current by four orders of magnitude confirming experimental results. The results indicate that the increase of MoS2 layer numbers leads to a higher ${I}_{ \mathrm{\scriptscriptstyle ON}}/I_{ \mathrm{\scriptscriptstyle OFF}}$ ratio but degrades the intrinsic gate-delay time. Furthermore, it can be observed from the results that as the ribbon width increases the ${I}_{ \mathrm{\scriptscriptstyle ON}}$ of device increases at the cost of a lower ${I}_{ \mathrm{\scriptscriptstyle ON}}/I_{ \mathrm{\scriptscriptstyle OFF}}$ ratio.