High-performance self-driven ultraviolet photodetector based on SnO2 p-n homojunction

Taking advantage of the high-quality p-type epitaxial SnO2:Mg film achieved in our previous study, a p-SnO2: Mg/n-SnO2 homojunction based ultraviolet photodetector was fabricated on a c-sapphire substrate by pulsed laser deposition in this work. The p-SnO2:Mg/n-SnO2 homojunction exhibits a typical diode behavior, with a rectifying ratio approaching 201 at 2 V and -2 V. Compared with the traditional metal-semiconductor-metal SnO2-based ultraviolet photodetector, the present p-n homojunction based photodetector is self-powered under 0 V bias. The built-in electric field in the interface depletion region of the p-SnO2:Mg/n-SnO2 homojunction separates photogenerated electron-hole pairs rapidly, which renders the photodetector an ultra-fast response speed (tau r = 0.57 ms, tau d = 0.64 ms). In addition, the detector exhibits a maximum photocurrent Ip of 1.5 nA under illumination with 290 nm light at 1.177 mW/cm2. At the same time, it shows a higher responsivity of 1.55 mA/W, and a higher detectivity of 9.8 x 1010 Jones, than traditional detectors. These results imply great application potential of SnO2 homojunction for UV photodetectors as well as other power devices.