4H-SiC bipolar junction transistors with graded base doping profile

This work reports 4H-SiC bipolar junction transistor (BJT) results based upon our first intentionally graded base BJT wafer with both base and emitter epi-layers continuously grown in the same reactor. The 4H-SiC BJTs were designed to improve the common emitter current gain through the built-in electrical fields originating from the grading of the base doping. Continuouslygrown epi-layers are also believed to be the key to increasing carrier lifetime and high current gains. The 4H-SiC BJT wafer was grown in an Aixtron/Epigress VP508, a horizontal hot-wall chemical vapor deposition reactor using standard silane/propane chemistry and nitrogen and aluminum dopants. High performance 4H-SiC BJTs based on this initial non-optimized graded base doping have been demonstrated, including a 4H-SiC BJT with a DC current gain of ∼33, specific onresistance of 2.9 mΩ·cm², and blocking voltage VCEO of over 1000 V.