1/f noise and percolation in impurity bands in inversion layers

Current noise measurements on Si inversion layers in the region of the Na impurity band at 4.2K are presented. The measurements show that the observed 1/f noise is an intrinsic property of the hopping conduction and is not due to charge trapping as usually assumed. Na-related structure in the noise magnitude suggests that percolation effects can be important to hopping conduction.