A model was presented which described the compensation that was produced in semi-insulating 6H material by V doping. Undoped crystals that had been grown by using vapor transport methods frequently contained between 1017 and 5 x 1018/cm3 of uncompensated B acceptors. Upon adding V, the 3d1 electron of the V donor compensated the holes of the B centers. It was shown that, when V was present in concentrations greater than those of B, the Fermi level was pinned to the V donor level. Temperature-dependent Hall-effect measurements showed that this donor level was situated at 1.35eV below the conduction band minimum. Thermally stimulated current measurements of V-doped crystals showed that B was the main compensating center for the V impurity.

J.R.Jenny, M.Skowronski, W.C.Mitchel, H.M.Hobgood, R.C.Glass, G.Augustine, R.H.Hopkins: Journal of Applied Physics, 1995, 78[6], 3839-42