Dopant level freeze-out in 6H-SiC Schottky diodes and junctions

Admittance spectroscopy is shown to be a very convenient tool for analysing majority carrier traps. We have studied by this technique different n- and p-type 6H-SiC Schottky diodes and pn junctions for different net doping levels, N-type and p-type doping are obtained by nitrogen and aluminum respectively, For nitrogen, we have detected two energy levels at E/sub c/-82 meV and E/sub c/-137 meV, which are respectively attributed to hexagonal and cubic sites in 6H-SiC. For aluminum, we have generally detected a rather large variation in the measured activation energy. This variation is supposed to depend on the net doping level, that is, on the compensation ratio.