Origin of 1/f noise in bipolar transistors

In planar n-p-n transistors fabricated in IC technology, the dependence of 1/fnoise on the base current density jB, the base width WB, and the emitter area FEwas measured. The power spectrumS_{iB}(f)of the base current fluctuations iBcan be represented by the empirical relationS_{iB} = const. jmin{B}max{gamma} cdot Fmin{E}max{beta} cdot wmin{B}max{-1} cdot f^{-1}where1 leq gamma leq 2and β has been found to be 1.3 or 2. The results of measurements on gate-controlled devices indicate that 1/fnoise cannot be explained by McWhorter's surface model. Therefore, a new model is proposed which assumes resistance fluctuations in the base region as the cause of 1/fnoise in bipolar transistors. The model establishes the relation forS_{iB}(f)as well as the magnitude of the coefficients β and γ.