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

Abstract

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 ( ${R}_{\textsf {th}}$ ) of a fabricated DHBT with a $\textsf {0.35} \times \textsf {8.0}\,\,\mu \text{m}$ emitter is 62% lower than that of a DHBT with the same epitaxial layer structure on an InP substrate. Thanks to the lower ${R}_{\textsf {th}}$ , the DHBT operates at a collector current density ( ${J}_{C}$ ) of over 25 mA/ $\mu \text{m}^{\textsf {2}}$ without any lowering of current gain. The DHBT exhibits a record ${f}_{t}$ of 695 GHz at ${J}_{C}$ of 21 mA/ $\mu \text{m}^{\textsf {2}}$ owing to the reduced emitter charging time by suppressing the Kirk effect.