(Invited) Selective Area Etching and Doping of GaN for Power Electronics

Gallium Nitride (GaN)-based devices are very attractive candidates for next-generation high-power applications, due to the intrinsic material properties. However, the lack of selective-area doping technique in GaN greatly limits the design flexibility and device performance. Implant or diffusion of dopants into GaN are currently being pursued. Additionally, attempts of selective-area etching by reactive-ion etching (RIE) followed by regrowth doping have been reported by many groups; most of them reported defective electronic interfaces with very leakage characteristics. It was determined that the presence of highly energy ions, reactive chlorine species, and ultraviolet photons in RIE tend to generate both surface and sub-surface damages. Here, we report an alternative method of selective-area etching to overcome this barrier. Tertiarybutylchloride (TBCl) is employed as an in-situ chemical etchant of GaN in MOCVD to create smooth trenches, and to remove plasma etching-generated damages on the surface. Regrowth is performed right after the TBCl etching without breaking the vacuum. Several key issues that will be discussed include 1) the exploration of etching parameter space, 2) comparisons among continuous, RIE-etched, and TBCl-etched regrown PN diodes, 3) selective area etching and doping, 4) nanoscale characterization of selective area doping by scanning probes and atomic probe topography (APT), and 5) the implication of anisotropy in selective area regrowth. This work is supported by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000871 as part of the PNDIODES program managed by Dr. Isik Kizilyalli.