On the compensation mechanism in high-resistivity 6H–SiC doped with vanadium

A model is presented which describes the compensation mechanism resulting in semi-insulating 6H silicon carbide by vanadium doping. Undoped 6H–SiC crystals grown by physical vapor transport methods frequently contain between 1×1017 and 5×1018 cm−3 uncompensated boron acceptors. Upon addition of vanadium, the 3d1 electron of the vanadium donor compensates the holes of the boron centers. It is shown that when vanadium is present in concentrations greater than that of boron, the Fermi level is pinned to the vanadium donor level. From temperature dependent Hall effect measurements, this donor level has been determined to reside 1.35 eV below the conduction band minimum. Thermally stimulated current measurements on V-doped SiC crystals show that boron is the major compensating center for the vanadium impurity.