Broad Range (254–302 nm) and High Performance Ga<sub>2</sub>O<sub>3</sub>:SnO<sub>2</sub> Based Deep UV Photodetector
Arnab Mondal, Santu Nandi, Manoj K. Yadav, Arpit Nandi, Ankush Bag
Abstract
The harmful UV radiation leaking out of the ozone hole can have a detrimental effect on mother nature. To monitor any UV rays leaking out of the ozone hole requires an electronic device such as deep UV photodetectors. In this context, Sn-doped Ga<sub>2</sub>O<sub>3</sub> incorporated with SnO<sub>2</sub> nanostructures has been grown on a c-plane sapphire substrate using low-pressure chemical vapor deposition (LPCVD) followed by the fabrication of metal-semiconductor-metal (MSM) based deep ultraviolet (UV) photodetector (PD) using Pt as electrodes with interdigitated geometry. The PD possesses a low dark current of 21 nA even at 50 V bias with a very high photo-to-dark current ratio of 9 × 10<sup>4</sup> and exceptionally large responsivity of 1532 and 262 A/W under 254 nm and 302 nm UV-illumination respectively. Consequently, an extremely high detectivity of 1.7 × 10<sup>15</sup> Jones and external quantum efficiency of 7.4 × 10<sup>5</sup>% has been recorded under 254 nm illumination with a fast fall time of 0.2 sec. The PD works well in UV-B range with high responsivity and is attributed to the long wavelength absorption by the SnO<sub>2</sub> nanostructures accompanied by a charge transfer from SnO<sub>2</sub> to the Ga<sub>2</sub>O<sub>3</sub> layer. The high gain has been attributed to the photoconductive gain due to interface trapped charges and self-trapped holes, along with light trapping on the textured Ga<sub>2</sub>O<sub>3</sub> surface.