The Significance of Dislocation Density and Impurity Inhomogeneities to the Breakdown Characteristics of Production Run Planar Diodes

A study has been made of the effect of impurity striations and bulk dislocation density on the avalanche breakdown characteristics of production run planar diodes. The diodes were prepared from both Czochralski and floating-zone grown silicon possessing large differences in impurity striation magnitude. The results of the detailed V-I measurements were analyzed by computer methods to obtain numerican data on leakage current, breakdown sharpness, and breakdown voltage. This data was then subjected to statistical analysis to determine the significance of the bulk material properties with respect to the breakdown characteristics of the diodes. The results show that impurity striations produce very large variations in leakage current in addition to variations in breakdown voltage. There was also some indication that a large bulk dislocation density, such as occurs in floating-zone silicon, results in premature breakdown of a small percentage of the diodes. *This work was supported in part by the Defence Research Board of Canada through its Directorate of Industrial Research.