Al₂O₃/HfO₂ Bilayer Dielectric for Ambipolar SnO Thin-Film Transistors With Superior Operational Stability

In the past few years, ambipolar tin monoxide (SnO) thin-film transistors (TFTs) have been widely studied because of ever-increasing demands for simplifying CMOS circuit and fabrication of more compact CMOS devices. However, in view of the serious decline in device performance upon gate-bias stress and environmental exposure, it is urgent to develop an effective passivation strategy for improving the operational stability of SnO TFTs. Here, aluminum oxide (Al2O3)/hafnium oxide (HfO2) bilayer dielectric is employed as a passivation layer for achieving ambipolar SnO TFTs with greatly enhanced operational stability, in which the Al2O3 dielectric is used to reduce the interfacial trap states, while HfO2 dielectric can prevent the diffusion of water/oxygen. Furthermore, a complementarylike inverter is presented by simply connecting two identical ambipolar SnO TFTs, which can be maintained in ambient condition for more than four months with a voltage gain exceeding 30. The capacity to synchronously achieve fieldeffect conversion, operational stability, as well as logic function in ambipolar SnO TFTs opens up a rational avenue to the realization of compact logic circuits.