High current gain (>2000) of GaN/InGaN double heterojunction bipolar transistors using base regrowth of p-InGaN

GaN/InGaN double heterojunction bipolar transistors with a regrown p-InGaN extrinsic base have been fabricated on SiC substrates. The maximum common-emitter current gain exceeds 2000 at the collector current of 15 mA for a 50 μm×30 μm device. In addition, the offset voltage in the common-emitter current–voltage characteristics was reduced from 5 to 1 V. This indicates that the large offset voltage reported previously was mainly due to the degraded base ohmic characteristics. The regrowth of p-InGaN is effective for improving the characteristics of nitride heterojunction bipolar transistors.