Improvement of High-Frequency Characteristics of InGaAsSb-Base Double Heterojunction Bipolar Transistors by Inserting a Highly Doped GaAsSb Base Contact Layer

• Published in: IEEE electron device letters Vol. 36; no. 7; pp. 657 - 659
• Main Authors: Kashio, Norihide, Hoshi, Takuya, Kurishima, Kenji, Ida, Minoru, Matsuzaki, Hideaki
• Format: Journal Article
• Language: English
• Published: IEEE 01.07.2015
• Subjects: Conductivity; Doping; Double heterojunction bipolar transistors; double heterojunction bipolar transistors (DHBTs); Electrical resistance measurement; GaAsSb; highly doped base contact; Indium gallium arsenide; Indium phosphide; InP/InGaAsSb; Resistance; highly doped base contact; GaAsSb; double heterojunction bipolar transistors (DHBTs); InP/InGaAsSb
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2015.2429142

This letter presents InP/GaAsSb/InGaAsSb/InP double heterojunction bipolar transistors (DHBTs) with a highly doped base contact layer. In order to reduce the base contact resistivity, a 3-nm-thick highly doped GaAsSb contact layer is inserted between the InP emitter and 17-nm-thick composition- and doping-graded InGaAsSb base. Fabricated DHBTs with a 0.25-μm emitter show a current gain of 32 and a high open-base breakdown voltage BVCEO of 5.2 V. The DHBTs also exhibit fT/f max = 513/637 GHz at a collector current density of 9.5 mA/μm 2 and VCE = 1 V. The f max is higher by 124 GHz than that for InP/InGaAsSb DHBTs without the GaAsSb contact layer. These results indicate that the use of the GaAsSb/InGaAsSb base structure is very effective in improving f max .