Growth and doping of bulk GaN by hydride vapor phase epitaxy

Doping is essential in the growth of bulk GaN substrates, which could help control the electrical properties to meet the requirements of various types of GaN-based devices. The progresses in the growth of undoped, Si-doped, Ge-doped, Fe-doped, and highly pure GaN by hydride vapor phase epitaxy (HVPE) are reviewed in this article. The growth technology and precursors of each type of doping are introduced. Besides, the influence of doping on the optical and electrical properties of GaN are presented in detail. Furthermore, the problems caused by doping, as well as the methods to solve them are also discussed. At last, highly pure GaN is briefly introduced, which points out a new way to realize high-purity semi-insulating (HPSI) GaN.