Over 450-GHz \(f_{\mathit {t}}\) and \(f_{\mathrm {max}}\) InP/InGaAs DHBTs With a Passivation Ledge Fabricated by Utilizing SiN/SiO sub(2) Sidewall Spacers

• Published in: IEEE transactions on electron devices Vol. 61; no. 10; pp. 3423 - 3428
• Main Authors: Kashio, Norihide, Kurishima, Kenji, Ida, Minoru, Matsuzaki, Hideaki
• Format: Journal Article
• Language: English
• Published: 01.10.2014
• Subjects: Devices; Emittance; Gain; Indium phosphides; Ledges; Passivation; Silicon dioxide; Spacers
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2014.2349872

This paper describes InP/InGaAs double heterojunction bipolar transistor (HBT) technology that uses SiN/SiO sub(2) sidewall spacers. This technology enables the formation of ledge passivation and narrow base metals by i-line lithography. With this process, HBTs with various emitter sizes and emitter-base (EB) spacings can be fabricated on the same wafer. The impact of the emitter size and EB spacing on the current gain and high-frequency characteristics is investigated. The reduction of the current gain is <5% even though the emitter width decreases from 0.5 to \(0.25~\mu \) m. A high current gain of over 40 is maintained even for a 0.25- \(\mu \) m emitter HBT. The HBTs with emitter widths ranging from 0.25 to \(0.5~\mu \) m also provide peak f \(_{t}\) of over 430 GHz. On the other hand, peak f \(_{\max }\) greatly increases from 330 to 464 GHz with decreasing emitter width from 0.5 to 0.25 \(\mu \) m. These results indicate that the 0.25- \(\mu \) m emitter HBT with the ledge passivaiton exhibits balanced high-frequency performance (f \(_{t } = 452\) GHz and f \(_{\max } = 464\) GHz), while maintaining a current gain of over 40.