A STUDY OF THE THIN FILM TRANSISTOR
Date
1968-03
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Degree Level
Doctoral
Abstract
The thin film transistor appears to have significant potential. However, its practical applications are severly limited by difficulties which exist with the present device which arise from the fact that insufficient information is available concerning the 'UT. The most formidable problem is that of the device's electrical instability. It was the aim of this work to provide some of the required information.
Two distinct forms of instability were observed in the TFT; a positive and negative drift. The positive drift was accounted for by a model which invokes mobile insulator ions. The observed asymmetrical drift rate observed with an Al-CdSe-SiO2 system was accounted for by a difference in activation energy for the release of ions from insulator interface ionic traps. The activation energies were found to be 0.51 ev for the Al-SiO2 interface, and 0.41 ev for the SiO2-CdSe interface. The traps widths were found to be 15 A and 13 A respectively. The presence of water vapour enhanced the magnitude and rate of the positive drift, but could not induce it if it was not present. The negative drift was accounted for by the presence of electron trapping states. These were found to be associated dominantly with the surfaces. A model was formulated in which one component was at the semiconductor-
insulator interface while a second component was in the insulator immediately next to the semiconductor. Electrons from the semiconductor tunneled into these with a time cons-tant which was an inverse exponential function of the distance of the trap from the interface.
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Degree
Doctor of Philosophy (Ph.D.)
Department
Electrical and Computer Engineering
Program
Electrical Engineering