A COMPREHENSIVE OPTICAL CHARACTERIZATION METHOD FOR HIGH-PERFORMANCE N-P-N ALGAAS-GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS

We report a comprehensive optical wafer evaluation technique for C-dop ed n-p-n heterojunction bipolar transistors (HBT) using low temperatur e photoluminescence spectroscopy, The correspondence between the optic ally determined parameters at the wafer level and the electrical devic e parameters is demonstrated, The hole density in the base of transist or structures was obtained from optical transitions in the p(+)-GaAs l ayer exploiting the bandgap narrowing effect, Furthermore, our experim ental studies, which combine optical and electrical measurements, show that a photovoltaic effect observed in the optical spectrum measures the strength of carrier recombination processes in the emitter-base he terojunction region, Because interface recombination strongly affects the de current gain of these devices, photoluminescence spectroscopy o f epitaxial wafers provides critical information on HBT device paramet ers prior to device fabrication.