Improved Environmental Stability of InSnO Thin-Film Transistor by Interface Engineering

To meet the demand for next-generation electronic products with excellent driving ability and high switching speed, using InSnO electrode material as a semiconductor channel layer is one of the attempts to improve the mobility of thin-film transistors (TFTs) However, instabilities in the environment limit the development of high-mobility semiconductors. In this work, an ultrathin hafnium (Hf)-doped InSnO (HITO) layer is prepared with enhanced stability, which is achieved by radio frequency magnetron cosputtering at low temperature. The HITO layer is deposited onto InSnO (ITO) to reduce the oxygen vacancies concentration, and thus, the trapping and detrapping issues at the surface of ITO channel are suppressed, leading to a high mobility of 76.21 cm $^{\text{2}}$ V $^{{-\text{1}}}$ s $^{-\text{1}}$ , a low threshold voltage of $-$ 0.86 V, and a steep subthreshold swing (SS) of 0.24 V/decade. The HITO layer is insensitive to water and oxygen and effectively blocks the permeability channel layer. The fabricated HITO/ITO TFTs obtain improved stability in positive bias stress (PBS) tests in humidity condition. The threshold voltage shifts under PBS at 85% relative humidity for 3600 s decreased from $-$ 8.2 to 0.97 V. This work provides a feasible method for low-cost, high-mobility oxide TFTs, and the whole process temperature control below 150 $^{\circ}$ C also expands its application in flexible electronic devices.