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 spectrumSiB(f)of the base current fluctuations iBcan be represented by the empirical relationSiB = const. jmin{B}max{γ} · Fmin{E}max{β} · wmin{B}max{-1} · f⁻¹where1 ≤ γ ≤ 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 forSiB(f)as well as the magnitude of the coefficients β and γ.