Technologies for normally-off GaN HEMTs

This chapter reviews the current technologies for normally-off GaN-based HEMTs. First, the HEMT "cascode" approach is briefly described, highlighting advantages and limitation of this design.Then, after illustrating the recessed gate HEMT and the fluorinate gate approach, the focus is put on the recessed gate hybrid metal insulator semiconductor high electron mobility transistor (MISHEMT) and on the p-GaN gate HEMT. These are today the most promising and robust approaches for normally-off GaN HEMTs. The most critical issues of these technologies (e.g. heterostructure design, gate dielectrics, and metal gates) are discussed in this chapter.