Date of Award

Fall 1998

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical Engineering

Committee Director

Ravindra P. Josbi

Committee Member

Arun Dharamsi

Committee Member

Andi Klein

Call Number for Print

Special Collections LD4331.E55 K39

Abstract

The current-voltage (I-V) characteristics and photoconductive behavior of semi-insulating GaAs (SI GaAs) high-power switches have been investigated by using a two-dimensional, time dependent, drift diffusion transport model. The dc current-voltage behavior as predicted by the results of this model was compared with available experimental data to evaluate the accuracy and validity of the model. The results show very good agreement, Next, research was carried out to investigate the behavior of the switches under high-field operation.

Simulations at high voltages emphasize on the two following processes: (a) The mechanism of impact ionization and the effect of this mechanism on device stability and "lock on" phenomena, (b) the role of barrier height inhomogeneities on current characteristics. The barrier height fluctuations and inhomogeneities at the contacts have been shown to exert a strong affect on the dark dc I-U characteristics. However, the impact of this mechanism under high-voltage photoexcitation condition seem to be minimal. The simulation results also lead to the conclusion that the mechanism of bulk impact ionization plays a very important role in persistent conductivity, and is responsible for "lock on" currents as well. Filamentary current behavior is also demonstrated, and shown to be distinct and separate from the "lock on" process. Spatial non-uniformities such as barrier height fluctuations, trap density variations, and nonuniform illumination are shown to be necessary for current filaments. Finally, discussions on the further research for a more comprehensive study such as the effects of nonuniform optical illumination, and some other parameters to increase the accuracy and stability of the switches are presented,

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DOI

10.25777/efwm-pw62

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