Oxygen partial pressure dependent sputtered copper oxide films for visible photodetectors

In this study, metal-semiconductor-metal (MSM) structured visible photodetectors based on Cu2-xO thin films are fabricated onto a SiO2/Si substrate via direct current (DC) reactive magnetron sputtering. The dependence of oxygen partial pressure (pO2) on the visible photodetector performance of the deposited Cu2-xO films has been studied. Here, Cu2-xO film thickness is found to decrease from 229 nm to 202 nm with increasing pO2 from 2.0% to 8.0%. X-ray diffraction (XRD) analysis confirmed the cubic structure of the Cu2O phase. The compositional analysis confirms that 6.0% pO2 film has more copper vacancies than 2.0% pO2 film. As-deposited films have grain-like morphology with a uniform surface. The energy bandgap of deposited films decreases with the increase of pO2 from 2.0% to 6.0% and further increases at 8.0% pO2. Current-voltage (I-V) curves of the Au/Cu2-xO/Au test-device showed ohmic contact between the metal (Au) and semiconductor (Cu2-xO) due to the lower barrier height. Among different pO2 samples, the film grown at 6.0% pO2 exhibited a maximum photocurrent of 20.23 µA and also quick rise and fall times (100 ms and 90 ms) even at lower power density (0.1283 mW/cm2), which are superior to other reported copper oxide-based visible photodetectors. The obtained results indicated that MSM planar structured Cu2-xO photodetector is suitable to serve for future low-cost optoelectronic applications.