Computational Study of the Effects of Channel Materials & Channel Orientations and Dimensional Effects on the Performance of Nanowire FETs

Abstract

Silicon has been extensively studied for decades due to its successful applications in semiconducting devices such as metal-oxide-semiconductor field-effect-transistors (MOSFETs). With the demand for high performance devices and packing density, scaling of Si based MOSFETs was drastically driven into nano-scale regime. However, quantum tunneling starts play an important role in degrading the device performance of a conventional Si MOSFET, such as drain-induced barrier-lowering (DIBL) in nano-scale regime. Furthermore, silicon based devices will face its own physical limitation in near future (ITRS, 2007) due to this. Therefore, in order to overcome the challenges of scaling limitation, search for other potential channel materials, such as high carrier mobility material and structure modification have been the heart of research. Among the various proposed materials and device structures, gate-all-around (GGA) Si nanowire (NW) fieldeffect-transistors (FETs) stand out because their perfect surrounding gates enhance the ability of gate control to suppress the problem of DIBL and fully compatible with Si based technology integration. With the successful fabrication of Si nanowires in the different laboratories (Singh, N. et. al., 2006), nanowires (NWs) have been extensively studied as they are promising for building blocks as nanowire MOSFETs (Cui, Y. et. al., 2003; Pecchia, A. et. al., 2007; Kumar, M. Jagadesh et. al., 2008; Wei, Lu & Lieber, C.M., 2006; Wei, Lu. et. al., 2008), nanophotonic systems (Greytak, A.B. et. al., 2005; Agarwal, R. & Lieber, C.M, (2006); Tian, B. et. al., 2007; McAlpine, M.C. et. al., 2004) and as biochemical sensors (Patolsky, F. & Lieber, C. M., 2005; Hahm, J. & Lieber, C. M., 2004; Cui, Y. et. al., 2001; Gengchiau, L. et. al., 2007). Recent advanced development reveals that physical properties of nanowires could be modified depending on the NW growth direction and diameter. This suggests that material structure such as channel orientations play an important role in device performance optimization. Coupled with the fact that besides silicon, other semiconductor materials such as germanium (Ge) demonstrates promising results (Wang, J. et. al., 2005; Rahman, A. et. al., 2005), a new chapter of study on alternate high mobility channels in nano world has been opened.