Electrical and Optical Properties of Transparent Conducting Homologous Compounds in the Indium–Gallium–Zinc Oxide System

Abstract

The homologous compounds In 1− x Ga 1+ x O 3 (ZnO) k (where k = 1, 2, or 3) were prepared at a temperature of 1400°C. The solubility limits (as determined via X‐ray diffractometry) were 0.47 < [In]/([In] + [Ga]) < 0.67 for the k = 1 member, 0.35 < [In]/([In]+[Ga]) < 0.77 for the k = 2 member, and 0.29 < [In]/([In]+[Ga]) < 1.00 for the k = 3 member. Four‐point‐conductivity and diffuse‐reflectance measurements were performed on as‐fired and reduced samples. The band gap that was determined from diffuse reflectance increased as the Ga 3+ content increased and k decreased. The conductivity increased as k decreased and the In 3+ content increased. A maximum conductivity of 250 S/cm was obtained for k = 3 and [In]/([In]+[Ga]) = 1 after reduction. The minimum absorption edge of 325 nm was obtained for k = 2 and [In]/([In]+[Ga]) = 0.35 prior to reduction. The potential for metastable phases in the In‐Ga‐Zn‐O system with enhanced transparent‐conducting properties has been discussed.