A Comparative Study of the Morphologies of Etch Pits in Semi-insulating Silicon Carbide Single Crystals

Contact less resistivity mapping, scanning electron microscope (SEM) and confocal laser microscope have been used to study the relationship of the resistivity and the etching behavior of the semi-insulating 6H-SiC wafer. Evidence is presented that the morphologies of the etch pits vary significantly with the impurity concentrations. The V impurity strongly affects the etch rates of edge, screw and mixed dislocations. For the dislocation containing the Burgers vector component of < 0001 >, its vertical etch rate is enhanced distinctly. In contrast, the horizontal etch rate becomes larger for the dislocation containing the Burgers vector component of < 11(2)over bar0 >. The shape of the etch pits reflects the Fermi level of the semi-insulating wafer and the net shallow impurity concentration.