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

Abstract

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 (Al ₂ O ₃ )/hafnium oxide (HfO ₂ ) bilayer dielectric is employed as a passivation layer for achieving ambipolar SnO TFTs with greatly enhanced operational stability, in which the Al ₂ O ₃ dielectric is used to reduce the interfacial trap states, while HfO ₂ dielectric can prevent the diffusion of water/oxygen. Furthermore, a complementary-like 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 field-effect conversion, operational stability, as well as logic function in ambipolar SnO TFTs opens up a rational avenue to the realization of compact logic circuits.