Enhanced UV-visible light photodetectors with a TiO2/Si heterojunction using band engineering

Abstract

A simple hydrothermal process involving thermal diffusion has been developed to synthesize almost vertical doped titanium dioxide (TiO₂) nanorod arrays on a silicon (Si) surface. The enhanced ultraviolet-visible (UV-vis) light photodetectors with a TiO₂/Si heterojunction were fabricated using band engineering, by doping indium (In) or nitrogen (N) in TiO₂ nanorod arrays. The photodiodes showed high quantum efficiencies of 200–400% under visible light illumination (e.g., 565 nm), and ∼16% with UV light (365 nm). Additionally, the N-doped TiO₂/Si devices, with a unilateral linearly graded junction, had greater rectification characteristics, lower dark current, better quantum efficiency and response to UV detection, and the In-doped TiO₂/Si heterojunction had a better multiplication factor for weak visible light detection, with a decreased electronic barrier and increased carrier concentration. These excellent results mean that doped TiO₂/Si heterojunctions will be useful for new UV-vis light detection enhanced photodiodes which do not require expensive auxiliary equipment, thus making them easy to use in applications involving portable and wearable equipment.