Z1/2- and EH6-Center in 4H-SiC: Not Identical Defects ?
Deep Level Transient Spectroscopy (DLTS) and Double-correlated DLTS (DDLTS) measurements have been conducted on Schottky contacts fabricated on n-type 4H-SiC epilayers using different contact metals in order to separate the EH6- and EH7-centers, which usually appear as a broad double peak in DLTS spectra. The activation energy of EH6 (EC - ET(EH6) = 1.203 eV) turns out to be independent of the electric field. As a consequence, EH6 is acceptor-like according to the missing Poole-Frenkel effect. Therefore, it can be excluded that the EH6-center and the prominent acceptor-like Z1/2-center belong to different charge states of the same microscopic defect as theoretically suggested. It is proposed that EH6 is a complex containing a carbon vacancy and another component available at high concentrations. The activation energy of EH7 (EC - ET(EH7) = 1.58 eV) has been evaluated indirectly by fitting the DLTS spectra of the EH6/7 double peak taking the previously determined parameters of EH6 into account.
Robert P. Devaty, Michael Dudley, T. Paul Chow and Philip G. Neudeck
B. Zippelius et al., "Z1/2- and EH6-Center in 4H-SiC: Not Identical Defects ?", Materials Science Forum, Vols. 717-720, pp. 251-254, 2012