The design, fabrication, and characterization of a novel electrode structure self-aligned HBT with a cutoff frequency of 45 GHz

This paper establishes a systematic approach for the design, fabrication, and modeling of a newly proposed self, aligned Al-GaAs/GaAs heterojunction bipolar transistor (HBT) employing a two-dimensional heterostructure device simulator and a heterojunction bi-polar 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 µm
²
two-emitter HBT exhibits a measured current gain cutoff frequency f
T
= 45 GHz and a maximum oscillation frequency f
max
= 18.5 GHz. 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.