Electron Tunneling through Thin Films of Aluminum Nitride

Citation

Lewicki, George Wladimir (1966) Electron Tunneling through Thin Films of Aluminum Nitride. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/QDH7-C768. https://resolver.caltech.edu/CaltechETD:etd-09272002-150142

Abstract

Thin film structures involving Aluminum as the base electrode, Aluminum Nitride as the insulating layer, Magnesium, Aluminum or Gold as the counterelectrodes were fabricated by nitriding a freshly deposited Aluminum film in a Nitrogen glow discharge with the thickness of the insulator varying from some thirty to ninety Angstroms with the express purpose of studying currents arising from the tunneling of electrons through the forbidden band of the insulator. Currents understood on the basis of the presently existing tunneling theory were observed for structures having thinner insulating regions. For structures having thicker insulating regions a temperature independent excess current was observed which could not be accounted for by the present tunneling theory. The usual analysis of tunneling assumes the energy momentum relation of the insulator forbidden band to be parabolic and the shape of the barrier separating the two metal electrodes to be trapezoidal. Any deviation from the current voltage characteristic predicted by this model is normally attributed to the lack of validity in the assumption concerning the barrier shape. Data obtained in this research indicated that the barriers of the structures investigated were trapezoidal but that the insulator energy momentum relationship was non-parabolic. Consequently, the analysis was extended to cover the case of a trapezoidal barrier with a semi-arbitrary energy momentum relationship. Greater freedom was obtained for the current voltage characteristics but certain relations between these characteristics and the insulator thickness were retained which could be used to determine whether or not the barrier of a particular structure was trapezoidal. These same relations also suggested a means of experimentally determining the insulator energy momentum relationship if the barrier could be considered trapezoidal. The analysis was applied to the experimental data and a complete self consistent model for electron tunneling through thin insulating layers of Aluminum Nitride was obtained.

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