Light-Dependent AC Transport Properties of Zinc Oxide (ZnO)/Reduced Graphene Oxide (rGO) Heterostructure Device: A Signature of Electrical Memory

We report the light-dependent AC transport properties of an ITO/ZnO/rGO/Au heterostructure from impedance spectroscopy measurements carried out at room temperature in the frequency range of 20 Hz to 50 MHz under dark light, white light, and red laser light with variable intensities. It has been observed that impedance is decreased with an increase in illuminating light intensities. The equivalent circuits have been considered for fitting the experimental ac responses that permit the isolation of exact resistance-capacitance (RC) contributions which can be attributed to the interface region. The diameter of the semicircles in Nyquist plots were found to decrease with the increase in illuminated light intensities, indicating transfer of charge carriers at the ITO/ZnO and ZnO/rGO interfaces. Here, interface resistances and capacitances were found to decrease and increase, respectively, with increases in incident light intensities. I-V measurements of our device have been performed under dark and red laser illumination condition. From the I-V measurements of our device, a photocurrent has been found to be directly proportional to the incident photon energy, and resistive switching behavior was also prominent at a high biasing voltage under illuminated conditions. We have also shown that electrical hysteresis in our device depends on the biasing voltage along with the incident light intensity. We believe such observations of our fabricated device seem to be promising for light energy-dependent photodetectors for multipurpose use.