Demonstration of SiC heterojunction bipolar transistors with AlN/GaN short-period superlattice widegap emitter

SiC bipolar-junction transistors (BJTs) are attractive candidates for high-power switching devices due to their high breakdown voltage and low on-resistance. However, SiC BJT has so far suffered from the limited current gain. An alternative device structure would be heterojunction bipolar transistors (HBTs). Because it is impossible to grow Si_xC_1-x solid solutions with x near 0.5, HBTs cannot be fabricated within group-IV semiconductors. Heteroepitaxial growth of wider bandgap group-III nitride (Al)GaN on SiC is one possible way to realize bandgap engineering in SiC devices. The fabrication of (Al)GaN/SiC HBTs was first reported by Pankove et al. followed by several groups. But any HBTs did not show common-emitter mode operation due to the large leakage at the emitterjunction.