Contents I. Introduction
Tunnel field effect transistors (TFETs) have appeared as a strong candidate for the next-generation low stand by power (LSTP) applications due to their sub-60-mV/dec subthreshold slope (SS) [1], [2]. However, the large indirect energy band gap of silicon makes it difficult to achieve low SS and high-ON current from the conventional silicon TFETs. As a result, alternative channel materials for the TFET are being investigated, which might have lower value of “least action integral” [3] and do not require phonon assistance for carrier tunneling. In the recent past, carbon-based materials especially carbon nanotube and graphene nanoribbon (GNR) find much attraction in the TFET applications [1], [4], [6]. Though the ultrahigh carrier mobility of the graphene has attracted extensive interest, its zero band gap feature has made it difficult for the transistor applications. Thus, opening and tailoring a band gap has become a highly pursued topic in the recent graphene research. A vertical external electric field can induce a tunable of up to 0.25eV for the bilayer graphene (GBL) [7], however, it also increases the carrier effective mass. Based on the GBL, recently, Fiori and Iannaccone [8] have proposed an ultra-low-voltage TFET. Earlier, it was investigated that, instead of GBL, a graphene-boron nitride heterobilayer (HBL) can produce quite higher and carrier mobility depending on their interlayer spacing and stacking pattern [9]–[11].
