Controlled conductivity of p-type CuxO/GaN piezoelectric generator to harvest very high piezoelectric potential

Typically, semiconductor piezoelectric-generators (PGs) exhibit low output potential because of the rapid screening by mobile carriers, and the output potential drops within fractions of a second. The reduction of internal carrier screening has been attempted by several groups, but complete suppression has not yet been reported. In this paper, a novel method for the fabrication of high-power PGs is presented. The detrimental screening issue was solved by fabricating a p-n heterojunction of p-type CuxO (x = 1, 2) and GaN. This was found to be an effective structure for decreasing the internal screening, while the suppression of screening was directly proportional to the resistivity of the p-type layer. The resistivity of the p-type thin film was controlled by optimizing the oxygen content in the environment during deposition. From X-ray diffraction analysis, the crystal structure of copper oxide changed by varying the oxygen incorporation, which primarily controlled the p-type conductivity. The optimized device exhibited output voltage of 26 V with a current density of 11.40 mu A cm(-2) under a pressure of 5 MPa. This study provides an effective approach for generating high electrical power, and it would be advantageous to construct flexible GaN PGs, which are essential devices for self-powered sensor networks. (C) 2017 Elsevier B.V. All rights reserved.