ABSTRACTWe report a photoreflectance (PR) characterization of InP/GaAsSb double-heterojunction bipolar transistor (DHBT) epitaxial wafers grown by metal-organic vapor-phase epitaxy (MOVPE). The origin of the Franz-Keldysh oscillations (FKOs) in the PR spectra was identified by step etching of the samples. FKOs from the InP emitter region were observed in the wafer with low recombination forward current at the emitter-base (E/B) heterojunction. In contrast, they did not appear when recombination current was dominant. The absence of the FKOs from the emitter indicates the high concentration of the recombination centers at the E/B heterojunction. We have also measured PR spectra from InAlP/GaAsSb/InP DHBT wafers. Pronounced FKOs from InAlP emitter reflect the suppression of recombination at E/B heterojunctions.