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Title: Electrical properties of polycrystalline semiconductor films
Author: Lile, Derek Lawrence
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1968
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The nucleation and structural details of evaporated layers of the compound semiconductors InSb and PbTe have been studied. To evaluate the electrical behaviour of these polycrystalline films as grown on amorphous substrates both resistivity and Hall voltage have been measured both as a function of deposition conditions and of temperature. Dynamic measurement of the high frequency differential capacitance associated with the surface space charge region on these materials when in contact with anodically formed A1203 has enabled the trapping behaviour of the surface region of these semiconductors to be determined across essentially the entire band gap. When combined with the results of field effect measurements a measure of the specularity to current carriers of these interfaces has also been obtained. Theoretical analysis of the surface measurements has required, for these narrow band gap materials, the use of degenerate statistics and in the case of InSb the inclusion of terms to account for the large non-paraboli - city of its conduction band. Because of the complexity of the resulting expressions their evaluation has been carried out on an IBM 7090 computer. Correlation between the surface and Hall results has been obtained and in the case of PbTe, as a result of its inordinately large value of permittivity, it is believed that the apparent intrinsic behaviour results from compensation of the bulk dopant by surface states. Thin film field-effect transistors have been fabricated from both InSb and PbTe. Both materials have proved reasonably successful in this respect but in the case of PbTe its large temperature sensitivity has indicated the inapplicability of its commercial exploitation. Dielectric trapping, the degrading effects of high resistance channel contacts and minority carrier conduction have been studied, the last apparently setting a fundamental limit on the device application of InSb.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available