Conference on Electrical Insulation and Dielectric Phenomena the 1983 J. B. Whitehead Memorial Lecture

The first theories of dielectric breakdown in solids derived expressions for critical fields that were intrinsic properties of the dielectric. These theories dealt with collision ionization from valence band to conduction band, but they did not consider the way in which the charges produced by the ionization would modify the electric field between the electrodes. It is the purpose of this review to follow some of the developments of space charge limited theories, especially in so far as they shed light on the thickness dependence of the breakdown strength.