Multi – wavelength photodetectors based on porous spin-coated and compact RF-sputtered NiO films grown over Si substrate: Effect of surface morphology

Abstract

Spin-coated and RF-sputtered NiO films were grown over Si substrate. FESEM analysis showed porous morphology for spin-coated NiO film and compact surface morphology for RF-sputtered NiO film. The photodetection properties were explored in metal-semiconductor-metal (MSM) configuration and were found to be greatly affected by the surface morphology of NiO. The responsivity of spin-coated NiO/Si PD was measured as 6.90, 3.68 and 4.39 A/W, whereas it was measured as 1.73, 1.81 and 2.07 A/W for RF-sputtered NiO/Si photodetector (PD), under exposure to 365, 625 and 850 nm lights, respectively. The photo-to-dark current ratio (PDCR) was calculated as 303, 172, 206 and 31, 35, 41 for spin-coated and RF-sputtered NiO/Si PDs, respectively. The higher photoresponse of spin-coated NiO/Si PD over RF-sputtered NiO/Si PD, especially at 365 nm wavelength, resulted from the larger surface area of porous structured spin-coated NiO film. Both PDs exhibited stable and repeatable photoresponse at different switching frequencies of the illumination source. The rise/fall time were estimated as 1.96/9.76 and 3.49/7.68 ms for spin-coated and RF-sputtered NiO/Si PDs, respectively.