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 48V and 51Cr 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 48Ti and 51V, respectively. In the case of 51Cr, three levels at 0.74, 0.18 and 0.15 eV below EC disappear with a time dependence of the nuclear decay, i.e. these levels are due to chromium. In the case of the 48V implantation, there is a comparatively strong tendency to form a compensated layer under identical implantation and annealing conditions. A level at EC — 0.97 eV is identified with vanadium in 4H SiC.