Fabrication and modeling of a novel self-Aligned AlGaAs/GaAs heterojunction bipolar transistor with a cutoff frequency of 45 GHz

This paper establishes a systematic approach for design, fabrication, and modeling of a newly proposed self-aligned AlGaAs/GaAs heterojunction bipolar transistor (HBT) employing a two-dimensional heterostructure device simulator and a heterojunction bipolar transistor circuit simulator. The developed HBT has an abrupt emitter-base heterojunction, and applies a novel structure in which a single base-electrode is placed between two emitter-electrodes. A fabricated 3 × 8 µm²two-emitter HBT exhibits a measured current gain cutoff frequency fT=45 GHz which is believed to be the highest, ever reported, for all kinds of bipolar transistors. Results of frequency divider circuit simulation indicate that the developed HBT would be 1.4 times faster than a conventional HBT in which one emitter-electrode is located between two base-electrodes.