A MODEL FOR LOW-FREQUENCY EXCESS NOISE IN SI-JFETS AT LOW BIAS

Spectral analyses of the fluctuating drain-source voltages in n- and p-channel Si-JFETs at low bias conditions revealed generation-recombination (G-R) noise over a temperature range of 150-300 K in both types of devices. The comer frequencies f(C) and the low frequency plateau values of the Lorentzian spectra were used to study the nature of the noise. In the n-channel device, f(C) was strongly temperature dependent; an activation energy, E(C) - E(T), of approximately 0.36 eV was obtained from the Arrhenius plot. For the p-channel device, a much higher corner frequency of 20-30 kHz was measured. Based on the experimental results we are led to consider a model for low frequency noise in JFETs that accounts for fluctuations in the channel thickness, and the correlated fluctuations in the number and the mobility of carriers. The relative significance of the three noise mechanisms was found to depend strongly on temperature, doping concentrations, device dimensions, and the energy level of the recombination centers.