High-Frequency Noise Modeling of InGaP/GaAs HBT With Base-Contact Capacitance and AC Current Crowding Effect

A heterojunction-bipolar-transistor (HBT) noise model including the base-impedance effect is presented, which takes into account the base-contact capacitance and ac current crowding effect. The proposed noise model describes well the high-frequency noise characteristics of InGaP/GaAs HBTs in the presence of base-impedance effect. Good agreement is observed between the measured and calculated noise parameters for the different sizes of InGaP/GaAs HBTs. We found that the effect of ac current crowding on noise parameters is more critical than that of base-contact capacitance.