Defect assisted magneto-tunable photoresponse in ZnO-rGO/La0.7Sr0.3MnO3/ITO heterojunctions

We have investigated light and magnetic field dependent electrical transport response of (100−x)%ZnO-x%rGO/La0.7Sr0.3MnO3 (LSMO)/ITO (x = 0, 100, 0.6, 0.8) heterostructure devices at room temperature. Negative and positive magnetoresistance(MR) response, respectively for bare (x = 0, 100) and composite devices (x = 0.6, 0.8) is associated with spin dependent scattering at eg 2↑ and t2g↓ band of LSMO space charge region. Positive bias current, for bare devices, is supposed to have a defect induced suppression with light leading to an overall decrease of device current at low field. However, the bias current may have started increasing with light at high fields thereby reversing photosensitivity sign from negative (NPS) to positive (PPS). Such reversal from NPS to PPS has been attributed to high defect induced carrier transport through depinning of electrons from weak pinning centers with magnetic field. (100−x)%ZnO-x%rGO/LSMO barrier widths that are directly proportional with defect state population seem to support field induced change of photosensitivity behavior with light illumination.