High-Speed InP/InGaAsSb DHBT on High-Thermal-Conductivity SiC Substrate

InP/InGaAsSb double heterojunction bipolar transistors (DHBTs) with an Au subcollector were fabricated on a SiC substrate by using a wafer bonding technique. The thermal resistance (R
_th
) of a fabricated DHBT with a 0.35 × 8.0 μm emitter is 62% lower than that of a DHBT with the same epitaxial layer structure on an InP substrate. Thanks to the lower R
_th
, the DHBT operates at a collector current density (J
_C
) of over 25 mA/μm
²
without any lowering of current gain. The DHBT exhibits a record f
_t
of 695 GHz at J
_c
of 21 mA/μm
²
owing to the reduced emitter charging time by suppressing the Kirk effect.