The centers, Fe3+, Fe2+, Fe+ and, probably the Fe0 center, were monitored via the Mössbauer absorption or emission spectroscopy of 57Fe-doped or 57Co-doped material; depending upon the experimental conditions. Isomer-shift measurements showed that the Fe bonds were more covalent here than in ZnS. Low-temperature Raman relaxation rates within the Fe2+ spin-orbit levels were found to be at least 100 times larger in ZnTe than in ZnS. A transient one-electron trap state, Fe+, was observed after electron capture decay of 57Co below 130K in stoichiometric ZnTe. The Fe+ → Fe2+ transition was shown to obey an activated process, with an associated energy of 0.09eV. A transient 2-electron trap state, Fe0, also seemed to have been detected as a precursor of the Fe+ state in low-temperature emission spectra. In ZnTe with enhanced p-type characteristics, the acceptor states (Fe+, Fe0) were no longer observed after 57Co decay, whereas a donor state, Fe3+, appeared.

C.Garcin, A.Gerard, P.Imbert: Journal of the Physics and Chemistry of Solids, 1990, 51[11], 1281-8