Improved device performance of rod like ZnO in a Schottky type photosensor compared to particle like ZnO: Analysis of charge transport

Abstract

In this work, we report two different synthesis process of semiconducting ZnO which modifies the morphology of the ZnO materials and its impact in photosensing Schottky diode. Hydrothermal and co-precipitation method were used to synthesize ZnO which gave rise to rod like (ZnO HT) and particle like ZnO (ZnO COP), respectively. From UV–Vis analysis, ZnO HT exhibited greater optical absorption. Al/ZnO (HT and COP)/ITO Schottky diodes were fabricated and the photoresponse as well as diode parameters were investigated by current-voltage and capacitance voltage measurements. Then charge transport properties were determined by space charge limited current theory and impedance spectroscopy. The results showed that the ZnO HT based SBD delivered a responsivity of 0.144 A/W which is 121% higher than the responsivity showed by ZnO COP based SBD (0.065 A/W). The specific detectivity of ZnO HT was measured at 7.54 × 109 Jones, a noticeable improvement from the 4.10 × 109 Jones of ZnO COP. The carrier mobility, lifetime and diffusion length of the ZnO HT based device were found to be 0.0014 cm2 V−1s−1, 72.35 μs and 72.37 μm respectively which are again superior to its counterpart. The faster and better charge transport is facilitated by the rod like morphology of the former. The study demonstrates improved device performance of rod like ZnO based Schottky diode and provides detail analysis of the Al/ZnO interface which can be beneficial for future research on metal-semiconductor junction.