Design of High-Performance Dual-Channel-Layered InGaZnO Thin-Film Transistors With Different Indium Contents

In this study, dual-channel-layered amorphous indium gallium zinc oxide (a-IGZO) based thin-film transistors (TFTs) with different In contents were fabricated using the RF magnetron sputtering technique to improve the performance and stability of single-layer a-IGZO TFTs. The optimum electrical performance of the dual-channel layered a-IGZO (2:1:1)/a-IGZO (1:1:1) TFT was obtained at a low V-TH of 0.5 V, I-on/I-off of 1 x 10(8), low subthreshold swing (SS) of 0.35 V/decade, high mu FE of 40.5 cm(2)/Vs, and best stability with small VTH shifts (1.4 and -1.2 V) under positive gate bias stress (PBS) and negative gate bias stress (NBS) test. This performance improvement, attributed to electron transfer from the a-IGZO (2:1:1) layer to the a-IGZO (1:1:1) layer, resulted in the accumulation of free carriers near at a-IGZO (2:1:1) and a-IGZO (1:1:1) interface. Thus, the charges were mainly concentrated within the barrier at the interface, improving performance (controlling VTH and Ne), while maintaining high mu FE in a-IGZO (2:1:1)/a-IGZO (1:1:1) TFTs. In addition, the oxygen interstitial defects (O;) of a-IGZO TFTs were calculated, and the inherent mechanism of stability improvement was examined. The degradation caused by O; increased with increasing In content in a-IGZO TFTs. Further analysis showed that dual-channel layered a-IGZO (2:1:1)/a-IGZO (1:1:1) TFTs significantly reduced O; and suppressed electron capture at the interface, resulting in enhanced device stability. Overall, the findings of this study are valuable for the advancement of dual-channel-layered a-IGZO TFTs.