Tunnel field-effect transistors based on van der Waals heterostructures are emerging device concepts for low-power applications, auguring $\mathrm{sub}\text{−}60\mathrm{mV}/\mathrm{dec}$ subthreshold swing values. In these devices, the channel is built from a stack of several different two-dimensional materials whose nature allows tailoring the band alignments and enables a good electrostatic control of the device. In this work, we propose a theoretical study of the variability of the performances of a ${\mathrm{MoS}}_2\text{−}{\mathrm{ZrS}}_2$ tunnel field-effect transistor induced by fluctuations of the relative position or the orientation of the layers. Our results indicate that although a steep subthreshold slope ($20\mathrm{mV}/\mathrm{dec}$) is achievable, fluctuations in the relative orientation of the ${\mathrm{ZrS}}_2$ layer with respect to the ${\mathrm{MoS}}_2$ one lead to a significant variability in the tunneling current by about one decade. This arises from changes in the orbital overlap between the layers and from the modulation of the transport direction.

• Received 7 February 2017

DOI:https://doi.org/10.1103/PhysRevApplied.8.034017