Flexible metal-oxide thin film transistor circuits for RFID and health patches

We discuss in this paper the present state and future perspectives of thin-film oxide transistors for flexible electronics. The application case that we focus on is a flexible health patch containing an analog sensor interface as well as digital electronics to transmit the acquired data wirelessly to a base station. We examine the electronic performance of amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) during mechanical bending. We discuss several ways to further boost the electronic transistor performance of n-type amorphous oxide semiconductors, by modifying the semiconductor or by improving the transistor architecture. We show analog and digital circuits constructed with several architectures, all based on n-type-only amorphous oxide technology. From circuit point of view, the discovery of a p-type amorphous semiconductor matching known n-type amorphous semiconductors would be of great importance. The present best-suited p-type is SnO, but it is poly-crystalline in nature and shows some ambipolarity due to the presence of n-type SnO2. In search of a better p-type semiconductor, preferably amorphous, we present recent insights into the band structure of potential amorphous oxide p-type semiconductors.