The physics of electrical breakdown and prebreakdown in solid dielectrics

We discuss physical models of high field phenomena in solid dielectrics. After a brief treatment of classical (thermal and electrostrictive) instabilities we turn to the discussion of current instabilities. We show that the strong nonlinearities in the current vs. voltage relation greatly simplify the picture. This is also true for avalanche breakdown where the carrier generation is strongly affected by selffields. We present experimental results for the energy and momentum loss functions for model dielectrics which allow to compute the critical field for impact ionization. The overall breakdown patterns are often tree-like and can be treated in terms of a fractal model. The review concludes with a short discussion of field induced ageing effects.