Microwave Noise Analysis in InP and GaAs HBTs

High frequency (h.f.) noise characteristics of advanced InP and GaAs HBTs were measured and simulated. The compact model (CM) HICUM/L2 v2.34 was used for the DC, AC and noise simulation as well as for the noise analysis. Geometry scalable model parameters for InP HBTs with the different emitter widths and lengths were extracted from temperature dependent DC and AC measurements on HBTs and special test structures. The CM is in good agreement with measured data. Non-equilibrium electron transport was found to shape fT and fmax for GaAs HBTs. For both HBT types, based on the noise source decomposition, an analysis of the influence of the different noise sources on the minimum noise figure (NFmin) was performed at different base-collector biases VBC. It was found that noise due to intervalley transfer related electron scattering has negligible impact on NFmin for both InP and GaAs HBTs. H.f. noise reduction as a result of Coulomb current blocking in GaAs HBTs was confirmed. Shot noise correlation was investigated in GaAs HBTs with different base layer thickness (wB) and base doping for the optimal h.f. noise behavior.