DEEP LEVELS OF CHROMIUM IN 4H-SIC

Deep levels of transition metals in 4H-SiC were investigated. A defini te chemical identification is achieved by observing the elemental tran smutation of radioactive isotopes. Epitaxial layers of n-type 4H-SiC w ere doped with the radioactive isotopes V-48 and Cr-51 by recoil impla ntation and subsequent furnace annealing at 1600 K. Repeated deep leve l transient spectroscopy (DLTS) measurements were performed during the elemental transmutation of these isotopes to Ti-48 and V-51, respecti vely. In the case of Cr-51, three levels at 0.74, 0.18 and 0.15 eV bel ow E-C disappear with a time dependence of the nuclear decay, i.e. the se levels are due to chromium. In the case of the V-48 implantation, t here is a comparatively strong tendency to form a compensated layer un der identical implantation and annealing conditions. A level at E-C - 0.97 eV is identified with vanadium in 4H SiC. (C) 1997 Elsevier Scien ce S.A.