High-mobility enhancement-mode thin-film transistors with 1.5 nm-thick ALD-grown Sn-doped In2O3 channels

Abstract

Aggressive channel thickness scaling to the sub-2 nm regime is essential for strengthening electrostatic gate control in monolithic three-dimensional electronics, but it causes severe carrier depletion and transport degradation in In2O3 thin-film transistors (TFTs). Here, we demonstrate enhancement-mode TFTs with 1.5 nm-thick Sn-doped In2O3 (ITO) channels prepared by inhibitor-assisted atomic layer deposition. At the same physical channel thickness, the ITO TFT exhibits a field-effect mobility of 25.7 ± 1.4 cm2V−1s−1, a subthreshold swing of 129 ± 31 mV/dec, and a threshold voltage of 0.2 ± 0.2 V, whereas the undoped In2O3 TFT undergoes severe transport degradation. The ITO TFT also shows markedly improved positive-bias-stress stability, with a threshold voltage shift of 0.37 V after 3600 s, whereas the thickness-matched In2O3 TFT reaches 2.07 V within 1000 s and fails before 3600 s. Analysis of the effective mobility and sheet carrier density indicates that Sn doping mitigates carrier depletion in the sub-2 nm channel. The resulting carrier replenishment improves on-state transport and strengthens electrostatic screening against positive-bias-induced trap charging, thereby improving the mobility–positive-bias-stress stability balance. These results establish controlled Sn doping as an effective strategy for realizing high-mobility ultrathin In2O3 TFTs with positive-bias-stress stability for monolithic three-dimensional electronics.