Temperature-dependent optical and electrical properties of InGaZnON thin films

Abstract

InGaZnON (IGZON) thin films are attracting considerable research interest for their role as the active layers in thin-film transistors (TFTs). Investigating the temperature-dependent optical and electrical properties of IGZON thin films is important for understanding the mechanisms underlying the temperature stabilities of IGZON TFTs in display applications and for developing new applications such as TFT-based temperature sensors and optical temperature sensors. This study is the first to investigate the temperature-dependent optical and electrical properties of IGZON thin films, using transmittance spectra and Hall measurements. Transmittance spectra were obtained between room temperature (RT) and 423 K. The absorption edge shifts to longer wavelengths (red-shift) from 16 to 25 nm as the temperature increases, while the sensitivity changes from 0.12 to 0.17 nm/℃. Free-carrier absorption increases with temperature and shows a linear dependence on the electrical conductivity (σ) and the free-carrier concentration (n). The optical band gap displays a negative linear dependence on temperature, with a coefficient ranging from -0.0007 to -0.001 eV/K. The results highlight the potential for applying IGZON thin films to optical temperature sensing. The carrier-transport properties were studied between 103 K and RT. Thermally-activated behavior in σ is apparent when n is less than 2×1019 cm-3 under non-degenerate conditions, described as σ = σ0 exp[-A/T1/4], characteristic of variable-range-hopping conduction. A linear σ-T relation is also visible, arising from weak-localization dominated by electron-electron interactions. At larger n, the behavior evolves toward degenerate conduction. Weak thermally activated behavior is displayed by the n and Hall mobility over the entire temperature range.