Near-Infrared Photodetection Using an Epsilon-Near-Zero Trapping Effect in Optimized Indium Tin Oxide Films

This paper investigates the unique optical and electrical properties of indium tin oxide (ITO) materials to achieve hot-carrier-based near-infrared photoelectric conversion utilizing the epsilon-near-zero (ENZ) light-trapping effect. By precisely controlling carrier concentrations via rapid thermal annealing (RTA), we optimized the optical and electronic characteristics of ITO, resulting in tunable ENZ wavelengths ranging from 1370 to 1600 nm as annealing temperatures increased from 400 to 500 °C. We propose a prism-coupled planar Au-ITO-Si stack designed to achieve high light absorption and enhanced photoelectric conversion efficiency by leveraging the ENZ effect. The device demonstrates a distinct photoelectric response with a cutoff wavelength of 1600 nm, and the ENZ effect is evident in the photoelectric response spectrum. A phenomenological model was developed to explain the processes involved in hot carrier (HCs) generation, transport, and emission. This work highlights the tunability of the ENZ wavelength achievable through annealing treatments and explores its potential applications in near-infrared photoelectric conversion through an effective device design.