The physics of electron devices is investigated within the framework of
Semiclassical Monte Carlo and Path-Sum Monte Carlo analysis. Analyses of shortchannel
III-V trigate nanowire and planar graphene FETs using a Semiclassical Monte
Carlo algorithm are provided. In the case of the nanowire FETs, the bandstructure and
scattering effects of a survey of materials on the drain current and carrier concentration
are investigated in comparison with Si FETs of the same geometry. It is shown that for
short channels, the drain current is predominantly determined by associated change in
carrier velocity, as opposed to changes in the carrier concentration within the channel.
For the graphene FETs, we demonstrate the effects of Zener tunneling and remote
charged impurities on the device performance. It is shown that, commensurate with
experimental evidence, the devices have great difficulty turning off as a result of the
Zener tunneling, and have a conductivity minimum which is affected by remote
impurities inducing charge puddling. Each material modeled is matched with
experimental data by calibrating the scattering rates with velocity-field curves. Material
and geometry specific parameters, models, and methods are described, while discussion
of the basic semiclassical Monte Carlo method is left to the extensive volume of
publications on the subject. Finally, a novel quantum Path-Sum Monte Carlo algorithm is described and applied to a test case of two layered 6 atom rings (to mimic graphene), to
demonstrate the effectiveness of the algorithm in reproducing phase transitions in
collective phenomena critical to possible beyond-CMOS devices. First, the method and
its implementation are detailed showing its advantages over conventional Path Integral
Monte Carlo and other Quantum Monte Carlo approaches. An exact solution of the
system within the framework of the algorithm is provided. A Fixed Node derivative of
the Path Sum Monte Carlo method is described as a work-around of the infamous
Fermion sign problem. Finally, the Fixed Node Path-Sum Monte Carlo algorithm is
implemented to a set of points showing the accuracy of the method and the ability to give
upper and lower bounds to the phase transition points. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/ETD-UT-2011-12-4436 |
| Date | 01 February 2012 |
| Creators | David, John Kuck |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Type | thesis |
| Format | application/pdf |
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