ABSTRACT
This chapter discusses the details of various GaN vertical devices, including two-terminal devices, such as PN diodes and Schottky diodes, and three-terminal devices, such as current aperture vertical electronic transistors (CAVETs), junction FETs (JFETs), and trench field-effect transistors (FETs). Ideally, at off-state breakdown a GaN vertical PN diode or a Schottky diode should be working in the punch-through mode. A number of different edge termination technologies have been tried for GaN PN diodes or Schottky diodes, including mesas, P+-GaN guard rings, high-resistivity layers created by ion implantation, and field plates. Besides the vertical JFET, a structure named "trench field-effect transistor" is also popular in three-terminal Si and SiC power devices. Similar to a vertical PN diode, the maximum threshold voltage (VT) of a vertical JFET is mainly determined by the wide bandgap of the material, that is, around 3.0 eV for a GaN JFET.
