An improved model for the GaAs HBT frequency performance under optical illumination

The theory and model for the GaAs heterojunction bipolar transistor (HBT) frequency performance under optical illumination are described. Photons absorbed in the base-collector depletion region, as well as those absorbed in the neutral base and collector regions are taken into account. The relative importance of these effects and their frequency performance are studied and estimations of the high-frequency photoresponse using PSPICE circuit simulations are shown.