Heterojunction channel engineering for enhanced mobility and stability of solution-processed holmium-doped indium oxide thin film transistors

In this study, a solution method was utilized to fabricate In2O3:Ho/In2O3 heterojunction channel thin film transistors (TFTs), and their electrical properties were compared with those of single-layer In2O3:Ho (HIO) TFTs. The threshold voltage shifts (Delta Vth) under negative bias illumination stress (NBIS) for the single-layer HIO TFTs showed improvement from -12.90 V to -1.25 V as the Ho doping content increased from 0 % to 10 %. However, this increase in doping content resulted in a decrease in mobility from 10.1 cm2v- 1s-1 to 1.6 cm2v- 1s-1. On the other hand, the In2O3:Ho/In2O3 heterojunction channel TFT exhibited an impressive mobility of up to 23.3 cm2v- 1s-1 and maintained excellent stability under NBIS conditions. Analysis of the band diagram obtained from ultraviolet photoelectron spectra and absorption spectra revealed the formation of a potential well with high electron density at the interface of the heterojunction. Upon application of a positive gate voltage (Vg), it became aligned with the built-in electric field of the potential well, resulting in an enhancement of its electric field and trapping more electrons within the potential well. This high electron density potential well acts as the primary transport channel for charge carriers, thereby significantly enhancing the mobility of In2O3:Ho/In2O3 heterojunction channel TFTs. Overall, our high-performance In2O3:Ho/In2O3 heterojunction channel TFT presents a promising avenue for advancing low-cost and large-area oxide electronics.