Metal-insulator transitions in IZO, IGZO, and ITZO films

摘要

In this study, we measured the low-temperature resistivity of amorphous two- and three-dimensional (2D and 3D) indium-zinc oxide, indium-gallium-zinc oxide, and indium-tin-zinc oxide films with a wide range of carrier densities. To determine their critical characteristics at the metal-insulator transition (MIT), we used the Ioffe–Regel criterion. We found that the MIT occurs in a narrow range between  = 0.13 and  = 0.25, where and are the Fermi wave number and electron mean free path, respectively. For films in the insulating region, we analyzed using a procedure proposed by Zabrodskii and Zinov'eva. This analysis confirmed the occurrence of Mott and Efros–Shklovskii (ES) variable-range hopping. The materials studied show crossover behavior from exp(T/T) or exp(T/T) for Mott hopping conduction to exp(T/T) for ES hopping conduction with decreasing temperature. For both 2D and 3D materials, we found that the relationship between T and T satisfies T ∝ T.