Statistical simulations of the low-frequency noise in polysilicon emitter bipolar transistors using a model based on generation-recombination centers

In this work, a new, physically based model for the low-frequency noise is investigated by statistical simulations, The proposed model is based only on superposition of generation-recombination centers, and can predict the frequency-, current- and area-dependence of the low-frequency noise, as well as the area-dependence of the variation in the noise level. Measurements on Bipolar Junction Transistors (BJTs) are found to be in excellent agreement with the simulated results. For devices with large emitter areas A(E), the model predicts a spectral density S-Ia similar to 1/f. For devices with submicron A(E), S-In strongly deviates from a 1/f behavior, and several generation-recombination centers dominate the spectrum. However, the average spectrum < S-IB >, calculated from several BJTs with identical A(E), has a frequency dependence similar to 1/f. The extracted areal trap density within the frequency range 1 - 10(4) Hz is n(T) = 3 x 10(9) cm(-2). The simulations show that the condition for observing g-r noise in the spectrum, strongly depends on the number of traps N-T, as well as the distribution of the corresponding energy level for the traps. The relative noise level is found to vary in a non-symmetrical way around < S-IB >, especially for small A(E). For A(E) < 0.1 mu m(2), the model predicts a relative variation in the noise level similar to A(E)(-2) below < S-IB >, and similar to A(E)(-0.5) above < S-IB >. For A(E) > 0.3 mu m(2), the variation is found to be similar to A(E)(-0.5).