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Abstruct-We have demonstrated self-aligned InGaP/GaAs heterojunction bipolar transistors (HBT's) with excellent dc, microwave, and noise performance. A 3 x 10 pm2 emitter finger device achieved a cutoff frequency of fr = 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 materia€ 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.

The effects of ex situ high temperature annealing (T≳500 °C) on the hole and hydrogen concentration of the base and on the dc device characteristics of InGaP/GaAs heterojunction bipolar transistors grown by low-pressure metalorganic chemical vapor deposition have been studied. Using rapid thermal annealing, hydrogen can be completely annealed out of the base, activating the carbon acceptors. Due to the low diffusivity of carbon, the high temperatures necessary to remove most of the hydrogen do not degrade the device characteristics. Using this simple technique to eliminate hydrogen from the base prior to device fabrication should improve the reliability of GaAs-based transistors with a carbon-doped base. Results also indicate that unlike carbon-doped In0.53Ga0.47As, hydrogen does not significantly affect the minority carrier characteristics of carbon-doped GaAs.