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Title: Computational study of shape, orientation and dimensional effects on the performance of nanowire fets
Keywords: Nanowire, Tight-binding, Top-of-barrier, ballistic transport, shape effect, size effect
Issue Date: 6-Jan-2010
Citation: KOONG CHEE SHIN (2010-01-06). Computational study of shape, orientation and dimensional effects on the performance of nanowire fets. ScholarBank@NUS Repository.
Abstract: In this research work, we evaluate the shape and size effects of Si and Ge nanowire (NW) field-effect-transistors (FETs) on device performance using sp3d5s* tight-binding (TB) model and semi-classical top-of-barrier ballistic transport model. This work is mainly divided into two parts: (a) to explore effect of orientation, focusing on circular NW, on FETs ultimate performance and (b) to investigate the effects of NW shapes on NW FETs ultimate performance. Firstly, we conclude that for n-type devices, [110] orientation gives highest On-state current compared to other orientations, regardless of channel material under study. We also observe that valley splitting is a strong function of quantum confinement, which is more significant for NW diameter smaller than 5 nm. In investigating the effects of gate capacitance on devices of different NW sizes, we conclude that gate capacitance degrades as the device shrinks into sub-nanometer regime. Secondly, our simulation results show that smaller cross-sectional area is desirable for high frequency device applications and for larger On-state currents, square cross-section may be desirable due to larger cross-sectional area and insulator capacitance. Furthermore, it is also observed that due to quantum effects, the ratio for small size NW FETs can be much less than one, rendering the classical assumptions and calculations invalid for nano-scale FETs. In this sub-nano region, therefore, a new set of assumptions and calculations in terms of effective mass, bandgap, and 1D density-of-states should be implemented as quantum effects start to play an important role in device performance.
Appears in Collections:Master's Theses (Open)

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