Investigation of optical and electrical properties of erbium-doped TiO₂ thin films for photodetector applications

We have investigated the electrical and optical properties of erbium (Er³⁺) doped TiO₂ thin films (Er:TiO₂ TFs) grown by sol–gel technique on glass and silicon substrates. The samples were characterized by field emission gun–scanning electron microscopes (FEG–SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), X-ray diffraction (XRD), photoluminescence (PL) and current–voltage measurement techniques. FEG–SEM and AFM images showed the morphological change in the structure of Er:TiO₂ TFs and EDX analysis confirmed the Er³⁺ doped into TiO₂ lattice. Broad PL emissions in visible and infrared regions were observed in undoped TiO₂ samples and associated to different mechanisms due to the anatase and rutile phases. PL spectra revealed sharp peaks at 525 nm, 565 nm, 667 nm and 1.54 µm which are related to Er³⁺ emissions in Er:TiO₂ samples. The undoped TiO₂ and Er:TiO₂ TFs based UV-photodetectors were fabricated, and various device parameters were investigated. The doped devices exhibit high photoresponse upon illuminating 350 nm UV light at 2 V bias with faster response time compared to undoped device.