SHALLOW LEVELS IN N-TYPE 6H-SILICON CARBIDE AS DETERMINED BY ADMITTANCE SPECTROSCOPY

Admittance spectroscopy has been used to study shallow levels in n-type 6H-SiC single crystals. A total of eight unintentionally doped n-type samples obtained from three different sources were used in this study. Two of the samples were grown by the Lely method, while the others were grown by physical vapor transport. Two electron traps at E(C)-0.04 eV and E(C)-0.03 eV were detected in the more heavily n-type (N(D)-N(A) = 10(18) cm-3) samples. These defects may be due to contaminants other than nitrogen. A defect level at E(C)-0.08 eV as detected in a sample with N(D)-N(A) = 8.9 X 10(17) cm-3. This level is associated with nitrogen at the hexagonal site (h). An electron trap at E(C)-0.11 eV was detected and is associated with nitrogen at the quasicubic sites (k1k2). This level was observed only in the lightly n-type samples (N(D)-N(A)=4.7 X 10(15)-6.4 X 10(17) cm-3).