A Low-Frequency Noise Model for Four-Gate Field-Effect Transistors

In this paper, a model is presented for the low-frequency noise in four-gate FETs (G4-FETs). It combines volume and surface noise sources. The generation recombination noise in the volume of the device originates from fluctuations of trapped charge in the depletion regions. We propose a model for calculating this noise component by evaluating the fluctuation in the cross section of the transistor conducting channel. Drain-current fluctuations due to trapping and detrapping of electrons at interface traps are also incorporated in the model and adapted for mixed surface-volume conduction. The global power spectral density of the drain-current, including both noise sources, is evaluated in different operating modes of the transistor. Our numerical results show good agreement with the experimental results of other authors. A study of the different kinds of center in the semiconductor (traps and recombination centers) allows the interpretation of experimental data. We explain the different trends observed, both numerically and experimentally, in the representation of the total noise current as a function of the drain-current in different operating modes.