Space-Charge Limited Currents in Insulating Materials

Abstract

THE modern theory of solids predicts that an electron can travel freely through the periodic potential field of a perfect crystal lattice provided that its energy lies within certain well-defined limits, or energy bands, which are characteristic of the crystal. A practical implication of this is that, if a sufficient number of such ‘free’ electrons can be introduced from a metal cathode into the allowed bands of an insulating crystal, it should be possible to obtain a space-charge limited current flowing through the crystal. Such a current flow would be analogous to the space-charge limited current which flows across the evacuated region between the cathode and anode in a thermionic vacuum diode.