DEVELOPMENT OF HIGH POWER NPN GAN/INGAN DOUBLE- HETEROJUNCTION BIPOLAR TANSISTOR Final Report

The Georgia Tech team developed state-of-the-art GaN heterojunction bipolar transistor (HBT) technology in this NSF program. Throughout the project period, baseline device fabrication and material growth techniques were actively studied and significant technological advancement was achieved in III-Nitride (III-N) HBT research. We successfully demonstrated high-current gain (> 100) InGaN HBT on sapphire substrates using a single-pass epitaxial layer growth approach. With the knowledge accumulated in the program, we also demonstrated GaN/InGaN HBTs that can handle ultra-high-d.c. power density > 3MW/cm 2 , a power density level that none of currently available transistor technologies have ever achieved. Leveraged by the advanced HBT development in this program, we also successfully demonstrated the first microwave IIIN HBTs with fT > 5 GHz. These breakthrough results are important milestones for GaN bipolar transistors to become viable transistor technology for next-generation high-power, high-frequency electronics.