HIGH-FMAX COLLECTOR-UP ALGAAS/GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS WITH A HEAVILY CARBON-DOPED BASE FABRICATED USING OXYGEN-ION IMPLANTATION

AlGaAs/GaAs collector-up HBT's with a heavily carbon-doped base layer were fabricated using oxygen-ion implantation and zinc diffusion. The high resistivity of the oxygen-ion implanted AlGaAs layer in the external emitter region effectively suppressed electron injection from the emitter, allowing collector current densities to reach values above 10(5) A/cm2. For a transistor with a 2-mum X 10-mum collector, f(T) was 70 GHz and f(max) was as high as 128 GHz. It was demonstrated by on-wafer measurements that the first power performance of collector-up HBT's resulted in maximum power-added efficiency as high as 63.4% at 3 GHz.