The current-voltage characteristics of a defect metal-oxide-semiconductor, (MOS) structure (e.g. after breakdown) can be explained by electron transport through localized states formed by broken bonds. The density of states decreases exponentially below the mobility threshold. Comparing the experimental I-V curve with the theoretical power dependence, a good agreement is found between the microcrack length (about 0.1-0.3 mu m) and the microdefect size in the silicon subsurface region.