Very high field phenomena in dielectrics

Understanding of very high field phenomena in polymeric dielectric is reviewed, based on the concepts of field-dependent conductivity and space charge limited field, which leads to the conclusion that the electric field distribution can be predicted with reasonable accuracy under high field conditions. Other phenomena, such as photon emission, cannot be predicted reliably, probably because the concepts underlying the entire theory, that of "traps" or "impurity levels," within the band gap, are not understood, i.e., while the theory is written in terms of such concepts, no convincing physical basis for these phenomena has been provided. This issue is discussed and some suggestions possible directions for future research are suggested.