Passivated indium oxide thin-film transistors with high field-effect mobility (128.3 cm² V⁻¹ s⁻¹) and low thermal budget (200 °C)

Here, we demonstrate a high-mobility indium oxide (In 2 O 3 ) thin-film transistor (TFT) with a sputtered alumina (Al 2 O 3 ) passivation layer (PVL) with a low thermal budget (200 °C). The sputtering process of the Al 2 O 3 PVL plays a positive role in improving the field-effect mobility ( µ FE ) and current on/off ratio ( I ON / I OFF ) performance of the In 2 O 3 TFTs. However, these enhancements are limited due to the high density of intrinsic trap defects in the In 2 O 3 channels, as reflected in their large hysteresis and poor bias stability. Treating the In 2 O 3 channel with oxygen (O 2 ) plasma prior to sputtering the Al 2 O 3 PVL results in notable improvements. Specifically, a high µ FE of 128.3 cm 2 V −1 s −1 , a high I ON / I OFF over 10 6 at V DS of 0.1 V, a small hysteresis of 0.03 V, and a negligible threshold voltage shift under negative bias stress are achieved in the passivated In 2 O 3 TFT (with O 2 plasma pretreatment), representing a significant improvement compared to the passivated In 2 O 3 TFT (without O 2 plasma pretreatment) and the unpassivated In 2 O 3 TFT. The remarkable reduction of intrinsic trap defects in the passivated In 2 O 3 TFT compensated by O 2 plasma is the primary mechanism underlying the improvement in µ FE and bias stability, as validated by x-ray photoelectron spectra, hysteresis analysis, and temperature-stress electrical characterizations. Plasma treatment effectively compensates for intrinsic trap defects in oxide semiconductor (OS) channels, when combined with sputter passivation, resulting in a significant enhancement of the overall performance of OS TFTs under low thermal budgets. This approach offers valuable insights into advancing OS TFTs with satisfactory driving capability and wide applicability.