Highly efficient and low-cost multispectral photodetector based on RF sputtered a-Si/Ti multilayer structure for Si-photonics applications

Abstract In this paper, a new cost-effective multispectral photodetector (PD) based on amorphous-silicon (a-Si)/titanium (Ti) multilayer structure, which achieves a high UV-Visible-NIR photoresponse is elaborated. A new design strategy based on combining FDTD (Finite Difference Time Domain) with GA (Genetic Algorithm) was used to determinate the a-Si/Ti multilayer geometry providing the highest photoresponsivity in UV, Visible and NIR regions. The optimized structure is then fabricated using RF magnetron sputtering technique. A comprehensive analysis of the photodetector electrical, optical and structural properties was carried out. The sputtered a-Si/Ti multilayer was characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and UV–visible-NIR absorption spectroscopy. The a-Si/Ti multilayer PD exhibits a high broadband absorbance of 80% over the UV and even NIR spectrum ranges [200–1100 nm]. Moreover, photoelectrical characterization showed that the developed device exhibits an improved responsivity under UV, Visible and NIR lights (1.9 A/W at 365 nm, 1.24 A/W at 550 nm and 0.93 A/W at 900 nm) and a high ION/IOFF ratio of 68 dB. The broadband multispectral photodetection property offered by the proposed a-Si/Ti multilayer PD opens a new route for the fabrication of promising alternative photodetectors for future high-performance and cost-effective optoelectronic systems.