InP/InGaAs DHBT technology using SiN/SiO2 sidewall spacers

This paper describes 0.25-μm-emitter InP/InGaAs DHBT technology that uses SiN/SiO² sidewall spacers. The technology enables the fabrication of HBTs with a passivation ledge (0.10-μm width) and narrow base metal (<; 0.25 μm). The fabricated HBT exhibits a high current gain of over 50 and an ft of 491 GHz at a collector current density of 18 mA/μm².