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

Abstract

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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> two-emitter HBT exhibits a measured current gain cutoff frequency f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> = 45 GHz and a maximum oscillation frequency f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> = 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.