IOSR Journal of Electronics and Communication Engineering (IOSR-JECE) e-ISSN: 2278-2834, p- ISSN: 2278-8735 Special Issue - AETM'16 148 | Page Simulation of Electrical Characteristics of Gate All around Silicon Nanowire Field Effect Transistor using Extended Hückel Theory Based Semi Empirical Approach Mayank Chakraverty 1 , Harisankar P S 2 , Vaibhav Ruparelia 3 1, 2, 3 ( RF Analog & Mixed Signal PDK Enablement, GLOBALFOUNDRIES, Bangalore, India) ABSTRACT : Gate All Around (GAA) FET stands out as one of the most promising FET designs to replace the currently planar MOSFETs due to its ability to provide better gate control and better immunity to short channel effects. .This paper reports the electrical characteristics of GAA Silicon Nanowire Field Effect Transistor obtained using Extended Huckel Theory based Semi Empirical Method. The physics behind the Semi Empirical method has been presented in brief. The nanowire transistor has been simulated with two different gate dielectrics (SiO 2 & ZrO 2 ) and the electrical characteristics resulting from the two structures have been compared for power efficiency. A comparison of off-state current and off-state channel conductance between the two nanowire transistor structures has been presented towards the end of the paper that demonstrates that ZrO 2 gate dielectric based silicon nanowire transistor is power efficient than its counterpart with SiO 2 gate dielectric.. Keywords – Gate All Around, MOSFETs, Semi Empirical, Extended Hückel, Nanowire, Gate Dielectric I. INTRODUCTION Nanowire (NW) FETs have been proposed and now studied by many research groups around the world. This is because, they are promising candidate to sustain the relentless progress in scaling of CMOS devices [1] [3]. Several key factors have contributed to the boom in NW research. First, semiconductor NWs can be prepared in high-yield with reproducible electronic properties as required for Very Large Scale integrated (VLSI) systems. Second, compared with “top–down” nanofabricated device structures, “bottom–up” synthesized NW materials offer well controlled size; that is at or beyond the limits of lithography. In addition, the crystalline structures, smooth surfaces and the ability to produce radial and axial NW hetero structures can reduce scattering. These results in higher carrier mobility when compared with nanofabricated samples with similar size. Finally, the body thickness (diameter) of NWs can be controlled down to well below 10 nm. Therefore, electrical integrity of NW-based electronics can be maintained even as the gate length is aggressively downscaled. This is a feature that has become increasingly difficult to achieve in conventional MOSFETs [3]. Gate All Around (GAA) SiNW FETs have attracted significant interest because of their excellent electrostatic integrity even at the nanoscale [8]. Various types of SiNW FETs are being explored as a promising candidate for future transistors replacing planar MOSFETs in logic and Dynamic Random Access Memory (DRAM) applications, and their fabrication is being studied either from top-down or bottom-up approaches [2] [7].Since silicon planar MOSFETs are approaching their scaling limits, new device designs are being explored to replace the existing planar technology. Among the possible new device designs are Double Gate (DG) FETs, FinFETs, Tri-Gate FETs and Omega- Gate FETs. The Silicon Nanowire GAA FET stands out as one of the most promising FET designs to replace the currently planar MOSFETs due to its ability to provide better gate control and better short channel performance [6]. Recent developments such as synthesis of highly ordered nanowires and fabrication of nanowires as small as 1nm in diameter have illustrated the progress possible in silicon nanowire technology. Silicon nanowire devices exhibit higher transconductance and more ideal sub threshold behavior with improved on-current, reduced off-current and lower sub threshold slope [9]. II. EXTENDED HÜCKEL THEORY BASED SEMI EMPIRICAL APPROACH The simulations carried out in this paper use ATK-Semi Empirical (ATK-SE) formalism. This ATK-SE formalism uses the Semi Empirical Extended Hückel model to calculate the transmission characteristics of the nanowire. The extended Hückel method is a semi empirical quantum chemistry method, developed by Roald Hoffmann since 1963. It is based on the Hückel method but, while the original Hückel method only considers pi