Effects of Carrier Concentration, Indium Content, and Crystallinity on the Electrical Properties of Indium-Tin-Zinc-Oxide Thin-Film Transistors

We report the effects of carrier concentration (NCH), indium (In) content, and crystallinity (X_c) on the electrical properties of indium-tin-zinc-oxide (ITZO) thin-film transistors (TFTs). The ITZO TFT with the lowest NCH, In content, and amorphous phase at the optimized oxygen flow rate has high field-effect mobility a (μ_FE) of 37.2 cm²/V·s, high ON/OFF current ratio (I_ON/I_OFF) of ~ 1×10⁷, and low subthreshold swing (S.S) of 0.93. With increasing NCH, In content, and X_c, μ_FE, I_ON/I_OFF, and S.S surprisingly degraded to 14.4 cm²/V·s, ~ 4×10⁴, and 4.01, respectively. Our high ITZO TFTs with μ_FE of 37.2 cm²/V·s, obtained thorough control of the N_CH, In content, and X_c, was suitable for application to next generation ultrahigh resolution displays as well as high frame rate displays.