Photoelectrochemical etching of n-type 4H silicon carbide

Photoelectrochemical etching of highly doped n-type 4H SiC in dilute hydrofluoric acid along different crystallographic orientations under low voltage and/or low current conditions is studied. Scanning electron microscope images show that anodization of the hexagonal polytype 4H SiC with subsequent pore formation proceeds anisotropically. It is proposed that under uv illumination the crystallographic planes terminated with silicon atoms are more resistant to electrolytic attack than the planes terminated with carbon and mixed silicon-carbon atoms. This model is used to explain the observed triangular-channel pore morphologies. A clear indication was found that the resultant pore structure does not depend on the direction of the external electric field applied to the sample. Electrical parameters recorded as part of the photoelectrochemical etching process are described and interpreted.