III-N High-Power Bipolar Transistors

We report state-of-the-art d.c. and RF performance of GaN/InGaN npn DHBTs grown by the MOCVD technology on sapphire substrates. The fabricated GaN/InGaN HBTs achieved a collector current density greater than 50 kA/cm2 and a d.c. current gain of 60 at the collector voltage of 13 V. A open-base collector-emitter breakdown voltage of greater than 90 V was measured. Using the same layer structure and device fabrication techniques, we also demonstrated state-of-the-art RF performance of GaN/InGaN HBTs with fT greater than 8 GHz and fmax greater than 1.8 GHz at the collector current density of 11 kA/cm2. These d.c. and RF measurement results demonstrated the capability and feasibility of III-N HBTs for high-power circuit applications.