Huge mobility enhancement of InSnZnO thin-film transistors via Al-induced microstructure regularization

Abstract

High-field-effect-mobility InSnZnO thin-film transistors (TFTs) are prepared through Al-induced microstructure regularization (AIMR) at an annealing temperature lower to 400 °C. Spherical crystalline particles are distributed throughout the back channel near the Al layer, while an amorphous phase still represents the front channel but with enhanced microstructure ordering. Especially, the packing density is distinctly increased, and oxygen vacancies are largely reduced. The optimized TFT exhibits excellent performance with a steep sub-threshold swing of 0.18 V/dec, a high on/off current ratio of 2.5 × 108, a threshold voltage of −0.21 V, and a small threshold voltage shift of −0.24 V under negative bias stress (−20 V, 3600 s), especially a remarkable field-effect mobility boosted to 53.2 cm2/V s compared to 19.1 cm2/V s for the TFT without the Al layer. After Al removal, the TFT performance shows no obvious degradation, implying good compatibility of the AIMR technique to the current device process.