Voltage Transfer Characteristics of CMOS-Like Inverters for Ambipolar SnO Thin-Film Transistors

The voltage transfer characteristics (VTC) of complementary metal-oxide-semiconductor (CMOS)-like inverter using ambipolar SnO-thin-film transistor were analyzed based on analytical simulation to extract ambipolar parameters such as majority/minority carrier mobility. The unbalanced majority carrier mobilities caused by the inferior electron mobility limited the inverter characteristics, and the minority carrier conduction resulted in non-full swing Z-shape VTC in the oxide-CMOS-like inverter. We found that a majority/minority carrier mobility ratio was a key parameter to improve the VTC by reducing the subgap defect states in SnO channel. We also fabricated 3-stage ring oscillator using the CMOS-like inverters and confirmed the ambipolar operation with positive/negative supply voltages.