High mobility and productivity of flexible In2O3 thin-film transistors on polyimide substrates via atmospheric pressure spatial atomic layer deposition

Abstract

We fabricate In2O3 films using atmospheric pressure spatial atomic layer deposition (AP S-ALD) and investigate their properties at various temperatures (150 °C–225 °C). As the temperature increased, the growth per cycle (GPC) increases, with the GPC and refractive index reaching values of 1.33 and 2.02, respectively, at 225 °C. The In2O3 thin film indicates a reduction in carrier concentration from 1.53 ± 1.37 × 1021 to 3.09 ± 0.53 × 1020 cm−3 as the temperature increased, and a decrease in the resistance from 3.55 ± 0.07 × 10−3 to 3.70 ± 0.01 × 10−4 Ω∙cm, which is attributed to a decrease in the impurity concentration (150 °C: 1.5 at.%; 175 °C: 1.0 at.%; 200 °C: N/A; 225 °C: N/A) and an increase in crystallinity. We use the In2O3 film as a channel layer in a top-gate bottom-contact thin-film transistor (TG-BC TFT). The device shows excellent performance characteristics, including a field-effect mobility of 69.8 cm2/V·s, a threshold voltage of −0.06 ± 0.22 V, and a subthreshold swing of 0.16 ± 0.01 V/decade. We successfully fabricated high-mobility TFTs and demonstrated their reliability via bias and 50,000 bending tests. The high-performance channel layer of the TFTs fabricated using AP S-ALD are promising for flexible applications.