High Voltage 4H-SiC Epitaxial Emitter BJTs using a Self-aligned Selectively Re-grown Base Contact

We demonstrate a novel self aligned selective re-growth based epitaxial emitter BJT and, for the first time, give evidence for the presence of conductivity modulation in SiC BJTs. The p+ contact region is selectively re-grown with Tantalum metal as the mask for the emitter mesa isolation etch after which it is carburized and used as a mask for the selective growth of p+ regions in the trenches. This makes the process self aligned. An isolation etch is then carried out to disconnect any sidewall contact between the p+ and the n+ regions. The devices were fabricated on two sets of drift layers: 1) 45μm, 1.1 x 10¹⁵ cm^-3, and 2) 12μm, 4 x 10¹⁵ cm^-3.