Recent progress of the p-type oxide thin films for transistor applications: Nickel oxide, Tin oxide, and Copper oxide

Over the past decade, many research groups have been striving to develop high-performance p-type switching oxide materials for implementing complementary metal–oxide–semiconductor (CMOS) thin film devices. However, realizing p-type oxide thin film transistors (TFTs) whose electrical properties are comparable to n-type oxide TFTs has been challenging. This is because of inherent characteristics of p-type oxide materials such as the high formation energy of native acceptors and high hole effective mass caused by localized hole transport path. Developing a p-type oxide with a delocalized hole transport pathway and low hole formation energy is crucial for the production of CMOS circuits utilizing oxide thin films. NiO, SnO, and CuOx are being actively studied as candidate materials that satisfy these requirements. This review discusses the latest advances in the synthesis method of p-type binary oxide thin films and the approach for electrical performance enhancement.