A. Shukla, R.C. Junghare, G.C. Patil
Visvesvaraya National Institute of Technology Nagpur,
Keywords: strain, silicene, nanoribbon, tight binding
Summary:Due to excellent mobility 2-D semiconductors such as graphene and molybdenum disulphide have been explored as a possible solution for smaller technology nodes. Silicene, a hexagonal analogue of graphene is an excellent choice, since it settles quite well with the existing silicon industry. The problem faced by 2-D materials is mainly due to zero bandgap, which is a major hindrance to the transistor operation. Naumis et al. did strain analysis on 2D semiconductors using first principle approach. Although, Lin et al. proposed tight binding analysis on strained silicene, this study explores the material physics using the first principles. Although tight binding models on silicene have been reported in the literature, to the best of our knowledge the strain effect on silicene has not been studied from device perspective. In this paper, we explore the effect of strain on the electronic transport in silicene nanoribbon transistor using tight binding model. The device structure are modeled and simulated using NanoTCAD ViDES simulator. In this structure, the channel length = 10 nm and the source and drain regions are also of 10 nm each. The application of strain changes the lattice constant, Fermi velocity and buckling height, which in turn changes the hopping energy.The impact of strain has also been modelled and incorporated in our simulation setup. Further, the simulations have also been carried out for both compressive and tensile strain. It has been found that, for lower VGS values due to compressive strain, the IDS is higher whereas at higher VGS values due to the tensile strain ID reduces. This variations in ID is also being observed from the log ID verses VGS characteristics. The increase in IDS at lower VGS is mainly because of the smaller bandgap, which results in larger leakage current. From transmission parameter characterstics it can be seen that as the strain increases, the tunneling also increases. In this work the on-state drive current (ION) has been extracted at VGS= 1 V and drain-to-source voltage (VDS) = 0.3 V whereas the off-state leakage current (IOFF) is extracted at VGS= 0 V and VDS= 0.3 V. It has been found that the ION/IOFF of the silicene transistor is ~10^2 for all the strain values. Furthermore, it has been observed that, at each value of strain there is ~10% increase in the bandgap, which is consistent with the predicted models for strain analysis on silicene. In addition to this, we also observed that higher strains produce higher ION.Thus, application of strain is essential and has a significant impact on the bandgap of 2D semiconductors and hence affects the transfer characteristics of the device.