A Schottky barrier is an electrostatic interface between a metal and a semiconductor that plays a vital role in many electronic devices. Schottky Barriers: An Overview opens with a brief review of the metal-semiconductor Schottky junction, the basic charge transport theory and the issues associated with these barriers. Additionally, the authors provide an overview of recent developments in the field of Schottky contacts to ZnO and related materials, such as ZnMgO, BeZnO, and BeMgZnO. Despite the fundamental importance of Schottky barrier height, the mechanisms which control the barrier formation are still far from understood. As such, for a better understanding of Schottky barriers and barrier height, the authors discuss various empirical models. In closing, AlGaN/GaN Schottky barrier diodes with and without in-situ silicon carbon nitride cap layers are investigated, with the fabricated SBD with a SiCN cap layer exhibiting improved electrical characteristics.