Molten KOH Etching with Na₂O₂ Additive for Dislocation Revelation in 4H-SiC Epilayers and Substrates

A novel etching solution using molten KOH with Na₂O₂ additive (KN etching) for dislocation revelation in 4H-SiC epilayers and substrates has been proposed. Threading screw and edge dislocations (TSDs and TEDs) have been clearly revealed as hexagonal etch pits differing in pit size, and basal plane dislocations (BPDs) as seashell-shaped pits. KN etching has provided a solution to the problem that KOH etching is not effective for dislocation identification in n⁺-4H-SiC. The influences of SiC off-axis angles, carrier concentrations, and growth techniques on the effectiveness of KN etching have also been investigated. It has been shown that KN etching is applicable to SiC epilayers and substrates with any off-axis angle from 0 to 8° and electron concentrations from 10¹⁵ to 10¹⁹ cm^-3.