Date of Award

2014

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Electrical and Computer Engineering

First Advisor

O'Leary, Stephen

Second Advisor

Muscedere, Roberto

Keywords

Applied sciences, Electron transport, Gallium nitride, Short channel devices, Thz cutofffrequency, Transient transport, Zinc oxide

Rights

CC BY-NC-ND 4.0

Abstract

In this thesis, the electron transport that occurs within two wide energy gap semiconductors, gallium nitride and zinc oxide, is considered. Electron transport within gallium arsenide is also examined, albeit primarily for benchmarking purposes. The over-arching goal of this thesis is to provide the materials community with tools for analysis and optimization to be used when evaluating the consequences of transient electron transport within these compound semiconductors. Providing fresh insights into the character of the electron transport within zinc oxide, with particular focus on the device implications, is another aim of this analysis. Initially, Monte Carlo electron transport simulation results are used for a comparative analysis of the transient electron transport that occurs within bulk zinc-blende gallium arsenide and bulk wurtzite gallium nitride. It is found that for both materials the electron drift velocity and the average electron energy field-dependent "settling times" are strongly correlated and that the electric field resulting in the shortest electron transit-time is a function of channel length. Then, the applicability of the semi-analytical approach of Shur in evaluating the transient electron transport response within gallium arsenide, gallium nitride, and zinc oxide is critically examined. In particular, a comparison with Monte Carlo results is performed in order to establish the utility of this approach as a tool in studying the transient electron transport response. Next, a Monte Carlo analysis of the electron transport within bulk wurtzite zinc oxide is performed. The applied electric field strength that ensures the minimum electron time-to-transit across a given channel length is determined. These results are then used in order to provide an upper bound on the potential performance of zinc oxide based devices. Finally, the utility of the semi-analytical approach of Shur, for the purposes of device design optimization, is considered for the specific case of bulk wurtzite ZnO. It is found that the results produced through the semi-analytical approach of Shur are, in many cases, imperceptibly different from those of the Monte Carlo simulations. This adds to the allure of the semi-analytical approach as a versatile tool for transient electron transport analyzes and device design.

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