Effect of Ti Doping to Maintain Structural Disorder in InOx-Based Thin-Film Transistors Fabricated by RF Magnetron Sputtering

Abstract

The effect of Ti doping in an indium oxide (InOx)-based semiconductor is investigated for the thin-film transistor (TFT) property and crystal structure of the film. InOx and Ti-doped InOx (InTiOx) films deposited by RF magnetron sputtering under the same O2 partial pressure conditions were systematically compared. The TFT behavior of the InOx showed higher conductivity than that of the InTiOx and was drastically changed to metallic conduction after annealing at 150 °C. Under the annealing conditions when the electrical transition to the metallic behavior occurred, the InOx film was crystallized. The X-ray diffraction analysis revealed that the shrinkage of the In2O3 unit cell is pronounced in the case of InOx films. Thus, Ti dopants may play the role as a suppressor for shrinkage of the unit cell, i.e. maintaining neighboring In–In distances, in addition to suppression of oxygen vacancies. The In–In distance, which is related to the overlapping of In 5s orbitals, is considered to be one of the key factor for which InOx-based materials are utilized as conducting films or semiconducting channels.