We demonstrate graded AlGaN/GaN heterojunction bipolar transistors (HBTs) with selective injection of minority carriers across a p-GaN base and patterned regrown base contacts. The selective injection design regulates minority carrier transport under emitter-base forward bias through a thin base region, while thick and highly doped p+ GaN regrown layers patterned alongside the thin base regions are utilized to lower the base contact resistance. With SiO2 employed as a spacer between the emitter and the p+ regrown layers, the device with an interdigitated emitter/base-contact stripe design displayed a maximum collector current density (IC) of 101 kA/cm2, a maximum current gain (β) of 70 at IC∼ 1 kA/cm2 and ∼ 11 for IC> 50 kA/cm2. The reported results demonstrate the potential of the selective injection approach to break the long-existing HBT design tradeoff between base resistance and current gain for next-generation radio frequency and mm-Wave applications.
@article{arxiv.2309.09886,
title = {Selective injection AlGaN/GaN heterojunction bipolar transistors with patterned regrown base contacts},
author = {Chandan Joishi and Sheikh Ifatur Rahman and Zhanbo Xia and Shahadat H. Sohel and Siddharth Rajan},
journal= {arXiv preprint arXiv:2309.09886},
year = {2023}
}