Incoherent tunneling of electrons from three to two dimensions: Observation of conductance oscillations in a metal-insulator-semiconductor structure

We have observed incoherent tunneling in AlZnSHg_1-xCdₓTe metal-insulator-semiconductor (MIS) capacitors below T~110 K. Under thermal equilibrium, both the conductance-voltage and capacitance-voltage characteristics show strong oscillations when the MIS is biased into the strong inversion regime. On the basis of the temperature dependence of oscillation amplitudes, we explain the data by the incoherent tunneling of electrons from the three-dimensional (3D) valence band in the p-type bulk Hg_1-xCdₓTe into 2D electronic subbands at the inversion interface, through deep traps. The observed oscillatory conductance comes from the reduced dimensionality of final tunneling states.