Abstract
High-quality GaAsSb epitaxial layers lattice-matched to InP are required to construct ultra-high-speed (f <sub>T</sub> >500GHz) InP/GaAsSb/InP double heterojunction bipolar transistors. The issues of achieving high-quality GaAsSb/InP heterostructures growth by gas source molecular beam epitaxy are reviewed. © 2007 IEEE.