MOCVD growth and device characterization of InP/GaAsSb/InP DHBTs with a GaAs spacer

This paper describes the impact of a GaAs spacer inserted between the InP emitter and GaAsSb base of InP/GaAsSb/InP double-heterojunction bipolar transistors (DHBTs) grown by metalorganic chemical vapor deposition. The GaAs spacer suppresses the incorporation of excess Sb atoms from the GaAsSb base into the InP emitter, which reduces the recombination current at the junction. The fabricated DHBTs with a 0.5-μm-wide emitter show dc current gain of over 90 at current density (J_C) of 10 mA/μm². The 0.25-μm-emitter DHBTs yield current-gain cut-off frequency (f_t) of 384 GHz and maximum oscillation frequency (f_max) of 264 GHz at JC of 14 mA/μm².