Zn-doped CdO effects on the optical, electrical and photoresponse properties of heterojunctions-based photodiodes

ZnO nanostructures have attracted great attention from researchers due to their interesting properties that include better crystallinity, high surface-area, improved electrical and optical properties. Furthermore, among the Transparent Conductive Oxide (TCO) family, CdO is one of the most attractive materials, as it can be used in a wide range of applications. Those intriguing properties make them highly desirable for various applications including photodiode. In this study, Al/Zn-CdO/p-Si/Al photodiodes were created with the CdO interfacial layer having pure and different contents of Zn (0, 0.1, 0.5, 2 and 4 at%) using the sol-gel spin coating method. All films were grown onto the p-type Si and glass to determine their electrical and optical properties. The effect of transparent Zn doped CdO photodiodes on their morphology, electrical and optical properties were investigated. The morphological characteristics and elemental compositions of prepared materials were examined by the SEM and EDX analyses. The obtained images indicated that the growth rate of the films was suppressed with the doping of Zn and presented a polycrystalline structure. The measurements of transmittance demonstrate that the coated films have well transparency value with the range of 80–85% in UV and visible zones. The optical bandgap of films evaluated by the linear fitting linearly increases with a dopant concentration of Zn and founded to be ranging from (1.9 – 2.37 eV). The current-voltage characteristics of fabricated photodiodes demonstrated good rectifying behaviour when CdO doped with Zn0.1 The photoelectrical and photovoltaic behaviour with their parameters presented. Furthermore, the highest photosensitivity of 3.6 × 10−4 was determined for Zn0.1. In the light of the obtained data, it was concluded that the produced Zn doped-CdO based device can be utilized in the optoelectronic applications, especially for the sensor and photodiode technology.