ON THE COMPENSATION MECHANISM IN HIGH-RESISTIVITY 6H-SIC DOPED WITH VANADIUM

A model is presented which describes the compensation mechanism result ing in semi-insulating 6H silicon carbide by vanadium doping. Undoped 6H-SiC crystals grown by physical vapor transport methods frequently c ontain between 1 X 10(17) and 5 X 10(18) cm(-3) uncompensated boron ac cepters. Upon addition of vanadium, the 3d(1) electron of the vanadium donor compensates the holes of the boron centers. It is shown that wh en vanadium is present in concentrations greater than that of boron, t he Fermi level is pinned to the vanadium donor level. From temperature dependent Hall effect measurements, this donor level has been determi ned to reside 1.35 eV below the conduction band minimum. Thermally sti mulated current measurements on V-doped SiC crystals show that boron i s the major compensating center for the vanadium impurity. (C) 1995 Am erican Institute of Physics.