Nonlinear Current‐Voltage Characteristics with Negative Resistance Observed at ZnO‐ZnO Single‐Contacts

Abstract

A couple of zinc oxide (ZnO) single crystals with single boundaries (ZnO‐ZnO single‐contacts) are fabricated by the traditional vapor reaction method and their electrical properties are characterized. The ZnO‐ZnO single‐contacts obtained show nonlinear current‐voltage (I‐V) characteristics without varistor‐forming constituents. Some of the ZnO‐ZnO single‐contacts show pronounced nonlinear I‐V characteristics with negative resistance. The I‐V characteristics of the ZnO‐ZnO single‐contacts are apparently similar to those of ZnO varistors; however, there are marked differences in the electric structure of the boundaries between the ZnO‐ZnO single‐contacts and ZnO varistors. The capacitance‐voltage (C‐V) relations of the ZnO‐ZnO single‐contacts are quite different from that of ZnO varistors and no evidence for the formation of double Schottky barriers at the boundary region are found. A very slow response to current stress is a feature of ZnO‐ZnO single‐contacts and it is suggested that any thermal processes including Joule heat would modify the carrier transport efficiency through the boundaries.