Surface Barriers on Zinc Oxide

Abstract

The surface barrier systems consisting of gold and palladium on chemically prepared zinc oxide have been investigated in detail. Surface barrier energies have been determined by photoresponse, forward current versus voltage, thermal activation energy, and capacitance-voltage methods. Agreement in barrier energies obtained by the four methods is excellent. The barrier energy for gold is 0.66 eV and for palladium is 0.60 eV. Forward current-voltage characteristics were in quantitative agreement with simple Bethe diode theory as modified by the presence of image force lowering. The reverse current-voltage characteristic is in quantitative agreement with that expected from the simple image force lowering of the barrier, over a bias range of from 0.1 to 3 V. Carrier concentration derived from resistivity and Hall measurements agreed with that obtained from capacitance-voltage measurements. We believe this represents the first comprehensive study where such quantitative consistency has been demonstrated on a compound semiconductor barrier system. Existence of a deep level trap is indicated via the effects on capacitance measurements.

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