Films of the high-performance solution-processed amorphous oxide semiconductor a-ZnIn4Sn4O15, grown from 2-methoxyethanol/ethanolamine solutions, were used to fabricate thin-film transistors (TFTs) in combination with an organic self-assembled nanodielectric as the gate insulator. This structurally dense-packed semiconductor composition with minimal Zn2+ incorporation strongly suppresses transistor off-currents without significant mobility degradation, and affords field-effect electron mobilities of ∼90 cm2 V-1 s-1 (104 cm2 V-1 s-1 maximum obtained for patterned ZITO films), with Ion/Ioff ratio ∼105, a subthreshhold swing of ∼0.2 V/dec, and operating voltage <2 V for patterned devices with W/L = 50. The microstructural and electronic properties of ZITO semiconductor film compositions in the range Zn9-2xIn xSnxO9+1.5x (x = 1-4) and ZnIn 8-xSnxO13+0.5x (x = 1-7) were systematically investigated to elucidate those factors which yield optimum mobility, I on/Ioff, and threshold voltage parameters. It is shown that structural relaxation and densification by In3+ and Sn 4+ mixing is effective in reducing carrier trap sites and in creating carrier-generating oxygen vacancies. In contrast to the above results for TFTs fabricated with the organic self-assembled nanodielectric, ZnIn 4Sn4O15 TFTs fabricated with SiO2 gate insulators exhibit electron mobilities of only ∼11 cm2 V-1 s-1 with Ion/Ioff ratios ∼105, and a subthreshhold swing of ∼9.5 V/dec.
ASJC Scopus subject areas
- Colloid and Surface Chemistry