The parallelization and vectorization of Monte Carlo algorithms for modelling
charge transport in semiconductor devices are considered. The standard ensemble
Monte Carlo simulation of a three parabolic band model for GaAs is first
presented as partial verification of the simulation. The model includes scattering
due to acoustic, polar-optical and intervalley phonons. This ensemble simulation
is extended to a full device simulation by the addition of real-space positions, and
solution for the electrostatic potential from the charge density distribution using
Poisson's equation. Poisson's equation was solved using the cloud-in-cell scheme
for charge assignment, finite differences for spatial discretization, and simultaneous
over-relaxation for solution. The particle movement (acceleration and scattering)
and the solution of Poisson's are both separately parallelized. The parallelization
techniques used in both parts are based on the use of semaphores for the protection
of shared resources and processor synchronization. The speed increase results for
parallelization with and without vectorization on the Ardent Titan II are presented.
The results show saturation due to memory access limitations at a speed increase of
approximately 3.3 times the serial case when four processors are used. Vectorization
alone provides a speed increase of approximately 1.6 times when compared with the
nonvectorized serial case. It is concluded that the speed increase achieved with
the Titan II is limited by memory access considerations and that this limitation is
likely to plague shared memory machines for the forseeable future. For the program
presented here, vectorization is concluded to provide a better speed increase
per day of development time than parallelization. However, when vectorization is
used in conjunction with parallelization, the speed increase due to vectorization is
negligible. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37306 |
| Date | 29 July 1992 |
| Creators | Huster, Carl R. |
| Contributors | Goodnick, Stephen M. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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