Surface carriers' concentration dynamics caused by a small alternating applied voltage

One of our previous papers was devoted to threshold voltage in MOSFETs and MODFETs viewed as a problem of nonlinear dynamics. The behavior of surface carriers' concentration under D.C. (direct current) applied voltage has been investigated in details. In this paper we went a step further and investigated the behavior of the same quantity under combined D.C. and A.C. (alternating current). As a main result emerged that it was impossible to cause small harmonic oscillations of surface carriers' concentration around some equilibrium value regardless of applied D.C. voltage and thus imposed operating regime.