Demonstration and analysis of ambipolar SnO inverter with high gain

Ambipolar materials offer a unique and simple route toward cost-effective complementary thin film circuits. SnO is one of the few metal oxide semiconductors that demonstrates ambipolar behavior. In this work, we demonstrated an ambipolar SnO inverter with record high inverter gain and corroborated our experimental results with a comprehensive analytical model. First, we developed ambipolar SnO thin film transistors (TFTs) with symmetric p-type and n-type conduction. Using these ambipolar SnO TFTs, we fabricated ambipolar SnO inverters. Our ambipolar SnO inverter shows a record gain of 432 (V/V), which is the highest reported among all ambipolar material systems. To understand our high inverter gain, we developed a comprehensive analytical model to analyze the transition region of an ambipolar inverter. Our analytical model showed an excellent match with our experiment results. Furthermore, our analytical model shows that to achieve a high inverter gain and a voltage transition point in the middle of the supply voltage range, we must minimize channel length modulation and match the p- and n-type behaviors of the ambipolar TFTs. By expanding our understanding of ambipolar inverter behavior, this work highlights the possibilities of ambipolar SnO TFTs for future high performance complementary thin film circuits.