Growth of nitride semiconductors and its application to heterojunction bipolar transistors

Nitride heterojunction bipolar transistors (HBTs) are promising for high-power and high-temperature applications. However, two major issues for nitride HBTs have been low current gains and large offset voltages. Recently, to resolve these two issues, we developed a technique for extrinsic base regrowth of p-InGaN which led to the successful fabrication of Npn-type GaN/InGaN HBTs with high current gains and low offset voltages. These GaN/InGaN HBTs have a low-resistivity p-InGaN base and wide-bandgap n-GaN collector. We demonstrated their high breakdown voltage characteristics as well as high current density characteristics. These characteristics indicate that GaN/InGaN HBTs are favorable for high-power electronic devices.