Resonance Tunneling Through Impurity States in Metal-Insulator-Metal Junctions

Abstract

Motivated by the recent work of Parker and Mead on the effects of impurity trapping states in Schottky barriers, a theory of resonance tunneling through adsorbed atoms in field emission is modified to treat resonance tunneling through isolated and uniformly distributed impurities in the insulating layer of a metal-insulator-metal tunnel junction. In analogy with the magnetic impurity tunneling theory of Appelbaum, the effects of resonant tunneling through impurity states open up new tunneling channels with a concomitant change of slope in the current-voltage characteristics. These changes should be apparent as definite structure in curves of dσ/dV versus voltage although depending upon the impurity concentrations and impurity level positions relative to the Fermi levels of the two metals, the height of the structure reflecting the impurity energy level spectrum may not rise above the noise level. In addition it is seen that the presence of impurities can alter the total conductance of a M-I-M tunnel junction. The new conductance versus voltage characteristics are calculated.