Carrier injecton and conduction under high fields in dielectrics

Long-term degradation and dielectric breakdown of large bandgap insulators is caused by a complex set of mutually influenced microscopic physical and chemical mechanisms. Electronic, thermal, chemical, mechanical and other effects cannot be separated a priori and the lifetime-limiting processes have to be established in each case under specified conditions, for a given material system. In this short overview, we summarize progress made in the past few years at Brown Boveri Research in two important subfields relevant to dielectric aging, namely charge injection and charge transport under high electrical field conditions. We do not wish to imply that the effects described in the following are always or predominantly the ones which limit the practical use of insulating systems. Nevertheless, they must be kept in mind as ever-present electronic effects occuring even in the most perfect insulators.