Electrical properties of ZnO-based photodetector prepared by room temperature DC unbalanced magnetron sputtering

We study electrical properties of ZnO thin films on p -Si (100) substrates as ultraviolet (UV) photodetector. ZnO films with thickness of ~400nm were deposited by room temperature (RT) DC unbalanced magnetron sputtering (DC-UBMS), and we also used ZnO film deposited at 260°C for the comparison. Metal-semiconductor-metal (MSM) planar structure was fabricated by using silver (Ag) contact on ZnO thin films as photodetector. X-ray diffraction (XRD) spectroscopy shows the amorphous structure of RT growth of ZnO thin films in contrast to relatively good crystallinity of ZnO film grown at 260°C. I-V characteristics of reverse-forward bias of UV photodetector were taken in dark and light conditions. As the results, amorphous phase of RT ZnO shows the high value of dark current and photocurrent. High stability of photo detection is also observable over the specific time as investigated by switching condition. In addition, we found that the mechanism of photo detection is strongly related to the oxygen adsorption on the ZnO surface. This study provides an alternative way to have a simple and high sensitive UV photodetector.