Peaked structure appearing in the field effect mobility of silicon MOS devices at liquid helium temperatures

Structure consisting of many weak peaks separated by approximately 0.2 V appears in the field effect mobility as a function of gate voltage of silicon MOS devices below 4K and grows with decreasing temperature. The structure is thought to be related to the sharpness of the Fermi level and to arise from the fluctuations in the density of states within the inversion layer.