Study of low frequency noise in advanced SiGe:C heterojunction bipolar transistors

The purpose of this work is to characterize and locate the low frequency noise sources in advanced SiGe:C Heterojunction Bipolar Transistor (HBTs) developed for mm-Wave and THz applications. Low frequency noise is studied over transistors with different emitter areas (A_e) and emitter perimeters (P_e) at different base current biases. The 1/f noise level shows a quadratic evolution with base current I_B and 1/A_e, dependence versus emitter areas. Moreover the 1/f noise level is found to be independent of the emitter perimeter P_e. It is found that the low frequency noise sources are homogenously distributed in the base-emitter region. The SPICE parameter K_F related to the 1/f noise amplitude as well as the figure of merit K_b are found to be among the best results published. For instance Kb values lower than 10^-10 μm² are found. Compare to others bipolar technologies, very good values of the ratio f_c/ft are found underlining the quality of this advanced one. A minority of the transistors, mainly for small emitter areas, are affected by the presence of generation-recombination (g-r) components.