Electroluminescence in ZnO varistors: Evidence for hole contributions to the breakdown mechanism

摘要

The previously postulated production of holes during the electrical breakdown of varistors has been directly verified. In some compositions band‐gap (3.2 eV) luminescence from the recombination of these holes with free electrons has been observed. The intensity of this luminescence is greater in varistor compositions exhibiting higher nonlinearity coefficients. It is also proportional to the square of the current which implies hole creation by impact ionization in the depletion region near the grain boundaries. This study used varistors of relatively simple chemical composition.