Defect Revelation and Evaluation of 4H Silicon Carbide by Optimized Molten KOH Etching Method

We have studied the defects on 4H-SiC substrates and epilayers by using molten KOH defect selective etching. It is found that adding Na2O2 into molten KOH at the etched temperature enables the revelation of dislocations on n+ and semi-insulating substrates, whereas purely molten KOH is sufficient to obtain good etched pattern on p+ substrates. Related statistical data on dislocation densities of n+, p+ and semi-insulating substrates are also presented. The morphological defects commonly observed on the epilayers are finally investigated and it is shown that some important structural features can be revealed by molten KOH method.