Point quantum contacts in disordered Si MOS structures with an inversion p-type channel:: Nonlinear behavior of the system in the longitudinal and transverse electric fields

The behavior of the lateral conductance G of mesoscopic Si-MOS structures with an inversion p-type channel and a high concentration of built-in charges of ions (N-t <= 3 x 10(12) cm(-2)) in the conditions of the insulator-metal percolation transition is discussed. The following features are observed in the dependences of G on the transverse (Vg) and longitudinal (V-g) voltages at temperatures >= 77 K: a quasi-plateau G(Vg) at G approximate to 2e(2)/h and a minimum G(V-d) at vertical bar V-d vertical bar < 0.1 V (G << e(2)/h). It is shown that the data obtained from the field effect are consistent with the results of calculations of the characteristics of the point quantum contact (the curvature parameters for the potential in the longitudinal and transverse directions are h omega(x) approximate to h omega(y) approximate to 10 meV) but are completely inconsistent with the value of h omega(x) = 300 meV determined from the dependence G(V-d). This discrepancy is related to nonlinearity of a system of quantum contacts with respect to the longitudinal and transverse electric fields. It is shown that the number of quantum contacts along the percolation path varies in the range 1 <= N <= 30 under the effect of an electric field.