Improved collector transit time with ballistic pipi-structure in the npn-AlGaAs/GaAs HBT

In this paper, we propose an improved npn-HBT with pipi-doping collector structure maximally utilizing ballistic transport property with modified electric field distribution in the collector-base space charge region. With pipi-HBT, we obtained significant reduction of /spl tau//sub scr/ compared with those of previously reported conventional and ballistic collector structure HBTs.