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A model for 1 f noise is developed that is based on fluctuations of the number of energy states associated with extended defects and the defect gradient. The tendency for the source of the states such as dislocations to equilibrate by diffusion leads to a 1 f spectral distribution of the effective number of states. When the states are near the Fermi level and active in processes such as carrier recombination or tunneling in semiconductor devices, the fluctuations appear as 1 f noise in voltage or current. The model is quantitative and predicts low noise for a very uniform density of defects or very small defect size. The Hooge dimensionless constant is identified in terms of the defect structure.

We performed 1ƒ noise measurements on n-channel Hg1−xCdxTe Metal-Insulator-Semiconductor Field-Effect Transistors (MISFETs) biased in linear and saturation regions of operation at 77 K. The cadmium mole fraction x was approximately 0.29 which corresponds to an energy band-gap of 0.24 eV at 77 K. Through the investigation of the dependence of drain voltage noise power spectral density on gate and drain bias, we estimated the insulator-semiconductor interface trap density as a function of energy. In this analysis, both the noise magnitude and the spectral shape was studied. The frequency span was from 150 Hz to 5 kHz. The noise behavior of the device was modeled using the modified McWhorter Model, originally developed for silicon FETs. The interface trap concentration values computed from the low-frequency noise measurements using the above model were found to agree closely with HgCdTeZnS interface properties measured by capacitance and conductance methods.