Characterization of 4H-SiC pn Structures with Unstable Excess Current

4H-SiC p+nn+ structures fabricated by implantation of Al into a commercial n-type 4H-SiC epitaxial layer doped to (3-5)Ÿ1015cm-3 have been studied. Structures with unstable excess forward current were characterized by electron beam induced current (EBIC) and secondary electron (SE) methods and by Auger-electron spectroscopy (AES). Numerous defects were found with a depth which exceed the thickness of the p+-layer. Also, it was demonstrated that the concentration of carbon on the SiC surface always exceeds that of silicon, which may be the reason for the initially unstable conductivity via the defects.