Electronic Processes in Au-CdS-In Diodes

Citation

Muller, Richard Stephen (1962) Electronic Processes in Au-CdS-In Diodes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/JF60-HN20. https://resolver.caltech.edu/CaltechTHESIS:08042011-100847730

Abstract

A study of various electronic processes in a class of solid-state diodes which function analogously to thermionic-emission vacuum tube rectifiers is made. For experimental work, such diodes were fabricated from an insulating crystal (cadmium sulfide) to which an ohmic contact (indium) and a blocking contact (gold) were affixed. The properties of the diodes that are most rigorously investigated are the equilibrium space-charge-limited current voltage characteristic, the behavior of the blocking contact under high reverse fields, and the capacitance dependence upon crystal trapping-state kinetics. Electron trapping is demonstrated to have a marked influence on most of the electronic properties of analogue diodes. Mathematical analysis based upon the premise that these traps are volume-distributed in the crystals of CdS is corroborated by the experimental results. An analytical method, which treats various trapping configurations with energy in a unified fashion, is employed to calculate the expected influence of traps on the space-charge-limited current characteristic. Correspondence of this analysis with experimental observations permits the deduction, in some cases, of trap densities and trap depths. The theoretical treatment of the influence of volume-distributed trapping states on terminal capacitance is also shown to be consistent with measurements designed to test the physical model. Use of this theory to interpret measured capacitance variation allowed the determination of some of the kinetic properties of trapping states, thus demonstrating a new technique for obtaining this information. Correspondence with the results from other methods is good. Trapping-state concentrations in actual crystals are shown to constrain practical solid-state analogue devices to very small dimensions.

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