As the conventional silicon metal-oxide-semiconductor field-effect transistor (MOSFET) approaches its scaling limits, many novel device structures are being extensively explored. Among them, the silicon nanowire transistor (SNWT) has attracted broad attention from both the semiconductor industry and academia. To understand device physics in depth and to assess the performance limits of SNWTs, simulation is becoming increasingly important. The objectives of this thesis are: 1) to theoretically explore the essential physics of SNWTs (e.g., electrostatics, transport and bandstructure) by performing computer-based simulations, and 2) to assess the performance limits and scaling potentials of SNWTs and to address the SNWT design issues. A full three dimensional, self-consistent, ballistic SNWT simulator has been developed based on the effective-mass approximation with which we have evaluated the upper performance limits of SNWTs with various cross-sections (i.e., triangular, rectangular and cylindrical). The results show that SNWTs provide better scaling capability than planar MOSFETs. A microscopic, quantum treatment of surface roughness scattering (SRS) in SNWTs has also been accomplished, and it shows that SRS is less important in SNWTs with small diameters than in planar MOSFETs. Finally, bandstructure effects in SNWTs with small diameters have been examined by using an empirical tight binding model, and a channel orientation optimization has been done for both silicon and germanium nanowire fieldeffect transistors.
Jing Wang received his PhD at Purdue University in August 2005.
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Purdue University, West Lafayette, IN