Enhancement of Responsivity and Sensitivity of p-Silicon/n-Zinc Oxide-Based Photodetector Using Titanium Dioxide Nanoparticles

Here we report band structure design, fabrication and characterization of a novel ultraviolet photodetector which functions based on the heterostructure between silicon, zinc Oxide, and titanium dioxide nanostructures. For this purpose, Zinc Oxide nanowires were grown on p-type (100) oriented silicon wafer by hydrothermal method and covered by a ~20nm film of titanium dioxide which were deposited by chemical vapor deposition (CVD) method. Results reveal that in forward bias, the shell titanium dioxide layer reduces the dark current and enhances the sensitivity of photodetector, while in reverse bias titanium dioxide layer increases the responsivity. Responsivity and sensitivity as high as 2.5 A/W and 0.95 are obtained in this work, respectively. In our structure, photocurrent showed a linear dependence to illumination intensity. This linearity together with short response time demonstrate that the titanium dioxide nanostructure lowered the effect of trap states on the photo-response of the device, therefore, the dominant role in photocurrent generation was found to be related to the band structure design of the device.