Deep levels of chromium in 4H-SiC

Deep levels of transition metals in 4H-SiC were investigated. A definite chemical identification is achieved by observing the elemental transmutation of radioactive isotopes. Epitaxial layers of n-type 4H-SiC were doped with the radioactive isotopes V-48 and Cr-51 by recoil implantation and subsequent furnace annealing at 1600 K. Repeated deep level transient spectroscopy (DLTS) measurements were performed during the elemental transmutation of these isotopes to Ti-48 and V-51, respectively. In the case of Cr-51, three levels at 0.74, 0.18 and 0.15 eV below E-C disappear with a time dependence of the nuclear decay, i.e. these levels are due to chromium. In the case of the V-48 implantation, there is a comparatively strong tendency to form a compensated layer under identical implantation and annealing conditions. A level at E-C - 0.97 eV is identified with vanadium in 4H SiC. (C) 1997 Elsevier Science S.A.