DESIGN STUDY OF ALGAAS/GAAS HBTS

Using the BIPOLE computer program, the frequency performance of AlGaAs/GaAs HBT&s was assessed, having different layouts, different doping profiles, and different layer thickness; the optimized design of HBT&s was studied; and the high current performance of HBT&s and polysilicon emitter transistors was compared. It is shown that no current crowding effect occurs at current densities less than 1 × 105 A/cm2 for the HBT with emitter stripe width SE < 3 µm, and the HBT current handling capability determined by the peak fT is larger than that of the polysilicon emitter transistor by more than 2 times. An optimized maximum oscillation frequency [FORMULA OMITTED] (where WBop is the optimum base width, SE is the emitter stripe width, both in micrometers) has been obtained for a typical process n-p-n AlGaAs/GaAs HBT having base doping of 1 × 1019 cm−3. © 1990 IEEE