Current-voltage characteristics and photovoltaic effect of a Au/ZnFe₂O₄/GaN Schottky junction

A Au/ZnFe2O4/GaN Schottky junction with a semiconducting heteroepitaxial ZnFe2O4 insertion layer was prepared by using a combined synthesis process of pulsed laser deposition and sputtering. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Schottky junction, as well as its photovoltaic effect, were investigated under dark conditions or ultraviolet (UV) or blue illumination. Insertion of the semiconducting ZnFe2O4 interlayer clearly induced an increase in the rectification ratio. Based on I-V measurements in a forward bias region, the barrier height and ideality factor of the Au/ZnFe2O4/GaN junction were estimated to be about 0.89 eV and 1.58, respectively. On the other hand, C-V measurement in a reversed bias region suggested a relatively larger barrier height of ∼1.32 eV. The Au/ZnFe2O4/GaN junction showed an open-circuit voltage of ∼0.5 V under UV light and a clear switching photocurrent behavior with UV ON/OFF. A schematic band model with two interfaces, Au/ZnFe2O4 and ZnFe2O4/GaN, was proposed to explain the measured barrier heights in forward and reverse bias regions.