ZnO with p-Type Doping: Recent Approaches and Applications

ZnO is a significant semiconductor material with the characteristics of direct band gap, large exciton binding energy, and easy growth of high-quality nanostructures, and it is widely used in various fields. However, obtaining high-quality p-type ZnO has become a significant obstacle to the wide application of ZnO. The research on p-ZnO started several decades ago and is regarded as the research focus. Many researchers have obtained high-quality p-ZnO by chemical vapor deposition (CVD) and physical vapor deposition (PVD). To obtain high-quality p-ZnO, researchers have used some "better" techniques to improve the crystal quality and mobility of p-ZnO, such as molecular beam epitaxy (MBE) and post-treatment. This review provides an overview of some methods for obtaining high-quality p-ZnO, such as increasing the acceptor concentration, shallowing acceptor energy levels, and reducing donor defects. In addition, we also review the applications of p-ZnO in LEDs, UV detectors, thin-film transistors, gas sensing, bionic materials, and other fields.