A comparison of low-frequency noise characteristics of silicon homojunction and III-V heterojunction bipolar transistors

The low-frequency noise generators in silicon homojunction and III-V heterojunction bipolar transistors are examined and compared in terms of an equivalent input noise current generator in the common-emitter configuration. The 1/f noise component of this generator has been found to depend on the base current as I_B^γ where γ~1.8 for the Si BJT´s and InP/InGaAs HBT´s with high current gains (β~50), and γ~1.1 for the AlGaAs/GaAs HBT´s with low current gains (4<β<12). Besides the 1/f noise component there exists a variety of deep-level related g-r noise components in all transistors. The 1/f noise spectral density when presented versus the base current density has been found to be the lowest in the case of InP/InGaAs HBT´s