BREAKDOWN PHENOMENA RELATED TO TRAPPING DETRAPPING PROCESSES IN WIDE BAND-GAP INSULATORS

Mechanisms of breakdown phenomena related to charge carrier trapping and detrapping are investigated in wide band gap insulators. Trapping occurs in potential wells due to the presence of polarization charge at the border of domains having different permittivities and conductivities. Findings in this work are related to (1) the calculation of the polarization energy of the medium surrounding a trapped charge, (2) the investigation of the mechanism of space charge destabilization; (3) the explanation of the breakdown mechanism from the polarization energy dissipated after detrapping. An experimental method to produce breakdowns is recalled. In this method electron trapping is produced under keV energy electron irradiation and the space charge destabilization is obtained under low energy electron irradiation. Depending on the experimental arrangement, the method allows to produce flashover or bulk breakdown. The formation of a plasma, the melting of the sample, the formation of treeing or thermal etched pits are observed.