Vapor-Deposited, Thin-Film Heterojunction Diodes

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Abstract
Deposited heterojunctions between semi‐insulating CdS thin films and insulating materials have been fabricated, and their characteristics studied. Excellent rectification properties are obtained in which contact‐field emission from the heterojunction carries the forward currents. Field emission of this type exhibits several characteristics which differ from the Schottky field emission. These differences stem from the nondegeneracy of the electron source in the heterojunction case. Correspondence between the theoretical predictions for the behavior of such emission, as derived in this paper, with observed temperature and voltage dependence is very good. The theory developed may account for the low value for the Richardson factor obtained experimentally for oxide‐coated vacuum emitters. The structures studied consist of Al contacting a film of deposited CdS roughly 1 μ in thickness. Three different insulating materials CdTe, Al2O3, and SiOx were used to form the thin insulating film between the CdS and the metallic counter electrode.