Effects of Yttrium Doping on a-IGZO Thin Films for Use as a Channel Layer in Thin-Film Transistors

Abstract

Amorphous In−Ga−Zn−O (a-IGZO) has been studied as a channel layer in thin-film transistors (TFTs). To improve the bias-induced instability of a-IGZO TFTs, we introduced yttrium with high bond enthalpy by magnetron co-sputtering system. The Y-doped a-IGZO (a-IGZO:Y) films show relatively lower carrier concentration and higher Hall mobility, which is due to the suppression of oxygen vacancies caused by Y doping. The a-IGZO:Y showed a relatively higher transmittance in the visible light region compared to non-doped IGZO, which could be due to the decrease of shallow defect levels caused by oxygen vacancy in the band gap. The a-IGZO without Y doping showed dramatic changes in electrical properties as times progressed (over 240 h); however, the a-IGZO:Y showed no significant changes. The a-IGZO:Y TFTs demonstrated a more stable driving mode as exhibited in the positive gate bias stress test even though the values of VTH and SS were slightly degraded.

Flexible and Transparent Thin-Film Transistors Based on Two-Dimensional Materials for Active-Matrix Display

“…However, the transmittance in this region still exceeded 70% at 550 nm, which indicates that the 2D TFTs are highly transparent in the visible range. It is difficult to achieve high transmittance in the visible range with other bulk materials such as metals, Si membranes, and oxides because of their high reflectance or limitations in terms of film thickness. − Metallic films less than 5 nm thick exhibit ∼50% transmittance at 550 nm, and it is difficult to exceed 90% even with metal nanowires. Oxide electrodes, such as indium tin oxide and indium zinc oxide, have high transmittance, but it is difficult to simultaneously achieve mechanical flexibility because of their low fracture strains .…”

Comprehensive investigation of sputtering deposition pressure effects on a-InGaZnO Schottky diodes

“…Although a-IGZO has attracted great commercial interest and all these studies have been conducted, there still needs to be more literature on its properties, and therefore a-IGZO needs to be developed. Relatively low semiconductor band gap (3.2 eV-3.5 eV), excess oxygen vacancies, poor stability, high rough surface, or abundance of film defects limit using a-IGZO in optoelectronic devices [28,29]. It is foreseen that the development of these features will allow a-IGZO to be used more in various optoelectronic devices, such as imaging, radio frequency identification, and display technologies.…”

Compositional Engineering of Hf‐Doped InZnSnO Films for High‐Performance and Stability Amorphous Oxide Semiconductor Thin Film Transistors

“…[35] Several elements with high bonding strength with oxygen, such as, gallium (Ga), zirconium (Zr), hafnium (Hf), and yttrium (Y), are adopted in the indium oxide channel material as an oxygen binder and a stabilizer of the channel layer. [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] Although several elements have been employed as stabilizer in oxide semiconductor channel-based TFTs, investigation of the stabilizing element in oxide semiconductor is still lacking. In particular, The Hf-doped indium zinc tin oxide (Hf:InZnSnO) channel for high performance and stable transparent thin film transistors (TFTs) is developed by using a simultaneous cosputtering of InZnSnO and HfO 2 targets.…”