Peculiarities of impact ionization of Impurity Al in SiC polytypes

摘要

The specific character of impact ionization of a small radius impurities was investigated in polytypes 6H-, 4H-, and 15R-SiC. The I-V characteristics of Al breakdown in 6H-, 4H-, and 15R-SiC in electrical field were studied. It was shown that at 77 K the impurity breakdown takes place only under the large impurity concentrations (three orders larger than that in Ge). The following data were obtained: the decreasing dependence of breakdown field due to the concentration increase, the absence of the low temperature breakdown at low impurity concentration, and gigantic enhancement of breakdown field when the field is parallel to the crystal axis.