High-Speed Low-Noise InGaP/GaAs Heterojunction Bipolar Transistors

We have demonstrated self-aligned InGaP/GaAs heterojunction bipolar transistors (HBT's) with excellent dc, microwave, and noise performance. A 3 × 10 μm2 emitter finger device achieved a cutoff frequency of f T= 66 GHz and a maximum’ frequency of oscillation of fmax = 109 GHz. A minimum noise. figure of 1.12 dB and an associated gain of 11 dB were measured at 4 GHz. These results are the highest combined fT+ fmax and the lowest noise figure reported for an InGaP/GaAs HBT and are attributed to material quality and the use of self-aligned base contacts. These data clearly demonstrate the viability of InGaP/GaAs HBT's for high-speed, low-noise circuit applications.