Performance analysis of planar Schottky photodiode based on nanostructured ZnO thin film grown by three different techniques

Abstract

Three different deposition techniques, hydrothermal, radio-frequency (RF) sputtering and vacuum coating techniques are utilized to prepare nanostructured ZnO thin films on p-type, boron doped, (100) Si substrates to fabricate planar Ag/ZnO/Al Schottky photodetectors. The surface topology and structural features of the nanostructured ZnO thin films were investigated by scanning electron microscope (SEM) and X-ray diffraction (XRD). The electrical performance of the as fabricated Ag/ZnO Schottky diodes were investigated by according to their current-voltage (I–V) characteristics within a bias voltage range from −2 to +2 V. The diode parameters such as saturation current, rectification ratio, and barrier height were estimated from the measured I–V characteristics. The study revealed that RF magnetron sputtering and vacuum thermal evaporation derived devices exhibit a lower turn on voltage and better rectification ratio compared with those of devices fabricated based on the hydrothermal method. On the other hand, the hydrothermal derived device offers a higher barrier height compared with that of other investigated devices. The UV detection properties of these photodetectors were investigated. Several important parameters, such as sensitivity, quantum efficiency and detectivity were explored. The study revealed that the sensitivity at −2 V for hydrothermal, RF sputtering, and vacuum evaporation devices, were 15.3, 6.5 and 2.8, respectively. The quantum efficiencies at -2 V for the hydrothermal, RF sputtering, and the vacuum derived Schottky photodetector were 98.8%, 84%, and 96.7%, respectively. The detectivities of hydrothermal, RF sputtering, and vacuum evaporation deposited devices at a voltage of −2 V were 7.66 × 1010 Jones, 5.03 × 1010 Jones, and 2.86 × 1010 Jones, respectively. These values suggest that the proposed nanostructured ZnO photodetectors can create new opportunities for lightweight, low cost and weak UV signal detection.