Picosecond optoelectronic measurement of S parameters and optical response of an AlGaAs/GaAs HBT

The S parameters of an AlGaAs/GaAs heterojunction bipolar transistor (HBT) are measured using a picosecond optoelectronic system. The measured S parameters show qualitatively good agreement with those obtained using a conventional vector network analyzer. The optical response of the HBT is also measured using this system by directly illuminating the base-collector region. Used as a phototransistors, the HBT shows pulse widths with full-width half-maximum (FWHM) as short at 15 ps.>