ABSTRACT
We have demonstrated the first AlGaN/GaN heterojunction bipolar transistor. The layer structures were grown by MOCVD on c-plane sapphire. The magnesium doped GaN base was nominally 2000 Å thick. Selective base regrowth was used to repair damage to the base and provide a lower extrinsic base sheet resistance. These initial devices show current gain as high as 3, and breakdown voltages greater than 40V. The low gain is believed to be caused by short minority carrier diffusion lengths in the base.
