GaAsSb is a promising material for the base of a new generation of Heterojunction Bipolar Transistors (HBT) on InP, as it is expected to allow the elaboration of high-speed digital circuits (80 to 100 Gbits/s). Emitter-base interfaces between GaAsSb and InP need to be well controlled to ensure good performance of the HBT, and this requires a careful analysis of both material and interface quality. Photoluminescence (PL) experiments as a function of temperature and of power excitation density, as well as photoreflectance (PR) measurements are performed on GaAsSb/InP heterostructures in order to get information about ordering and segregation effects in antimonide alloys.
From the PL recombination energy across the type II interface and at the GaAsSb band-edge, the band offset ΔEC between InP and GaAsSb is calculated. The evolution of the band to band PL recombination is studied as a function of temperature: the energy and intensity of the type I PL transition are shown to exhibit specific behaviors, which are typical of carrier localization effects in semiconductor alloys. At low temperature, the shape of the PR spectrum results in an atypical steplike background, which is analyzed as a band filling effect in consequence of the carrier localization on potential fluctuations.