Fabrication of Broadband UV MSM Photodetector Using Reactive Sputtered Nickel Oxide Film

Efficient ultraviolet (UV) photodetectors are of significant interest due to their wide area of applications, such as bio-sensing, communications, and military applications1-3 . In this work, a metal oxide semiconductor sandwiched between metal electrodes (MSM structure) was developed as a broadband UV photodetector. The MSM photodetectors has garnered lot of interest because of its simple fabrication design, large active area, low dark current facilitating fast response. The metal oxide used was p-type nickel oxide (NiO) deposited by DC magnetron sputtering technique on top of indium tin oxide (ITO). Reactive sputtering from a pure nickel target was used to deposit NiO and the effect of oxygen concentration on the morphological and optoelectronic properties of the NiO was investigated. ITO is capable of providing good electrical conductivity and charge transporting behaviour which supports low leakage current4 . It is a n-type degenerate semiconductor which is widely used for transparent conducting films. Among different metal oxides, NiO is a promising p�type semiconductor with wide band gap value (3.2 to 3.8 eV, depending on stoichiometry) 5 . In this study, we explore the fabrication and characterization of a UV photodetector using ITO and NiO heterojunction. The device performance will be optimized by varying oxygen concentration during deposition of NiO. The variation of oxygen will be done by keeping argon concentration constant. The DC magnetron sputtered NiO thin film, acts as the photosensitive layer. Silver electrodes were used as contacts for the two layers. Material characterization has been done using different techniques like XRD, SEM, UV-vis spectroscopy, Raman spectroscopy and photoluminescence spectroscopy while electrical characterization has been performed using I-V source meter and four probe. The fabricated device demonstrates good change in light to dark current at low applied biased voltage. In conclusion, the development of UV photodetectors using DC magnetron sputtered p-type NiO thin films represents an encouraging route in the realm of optoelectronics. The tunablility of NiO film properties at the interface with the ITO substrate provide further leverage for advancements in photon sensing.

1. Razeghi, M.; Rogalski, Journal of Applied Physics. Semiconductor ultraviolet detectors. 1996, 79 (10), 7433-7473. 2. Yu A Goldberg, Semicond. Sci. Technol. Semiconductor near-ultraviolet photoelectronics. 1999, 14 (7), R41. 3. Ohta, H.; Hosono, H. J. M. T., Materials Today.Transparent oxide optoelectronics. 2004, 7 (6), 42-51. 4. Kim, H.; Lee, G.-N.; Kim, Journal of Nanomaterials. Hybrid structures of ITO-nanowire�embedded ITO film for the enhanced Si photodetectors. 2018, 34(12), 2625-2629. 5. Hakim, A.; Hossain, J.; Khan, K. J. R. E., Renewable Energy. Temperature effect on the electrical properties of undoped NiO thin films. 2009, 34 (12), 2625-2629