Bifunctional Photovoltaic and Violet Electroluminescent Devices Based on $n\hbox {-}{\rm ZnO}/n\hbox {-}{\rm GaN}$ Heterojunctions

An n-ZnO/n-GaN heterojunction has been fabricated by depositing n-ZnO film onto an n-GaN/sapphire sub strate. A bifunctional photovoltaic (PV) and violet electroluminescent device based on n-ZnO/n-GaN heterojunction was obtained. As a PV cell, the device exhibits a clear PV behavior under AM 1.5 G simulated illumination (100 mW cm^-2). The power conversion efficiency is 0.57%. The open-circuit voltage and the short-circuit current are 1.12 V and 12.3 μA, respectively. As a light emitting diode, the device exhibits a violet emission peak centered at ~433 nm under a bias voltage, and the apparent violet light is easily observed with the naked eyes. The mechanism for the dual function heterojunction device has been discussed.