| The design, fabrication, and analysis of an aluminum gallium nitride/4H silicon carbide heterojunction bipolar transistor for power switching applications are discussed. Due to a number of processing improvements over previously reported AlGaN/SiC HBT's in the scientific literature, this device was able to demonstrate for the first time operation in common-emitter mode. The devices produced a common-emitter gain less than unity, and the reasons for this are thoroughly investigated. Preliminary experiments on AlGaN/4H-SiC heterojunction diodes are also discussed, in which the aluminum alloy fraction and SiC surface preparation were varied to investigate their effect on the hetero-interface quality. Optimization of a number of unit processes including unbuffered selective area growth and ohmic contact formation are reviewed. Future design and process improvements for the HBT's are proposed. |
