Magneto-optical measurements on H-implanted6HSiC

Magneto-optical measurements were made at 1.5, 4.2, and 27 °K on two kinds of luminescence spectra found in H-implanted $6H$ SiC. The two spectra, called primary and secondary, are generated by the same center in two different charge states, the center being an H atom bonded to a C atom at a Si vacancy. The secondary spectrum is due to recombination of an exciton weakly bound to a charged center. Its magnetic splitting are of the kind predicted by effective-mass theory, as developed by Thomas and Hopfield, with $g_h=2.8\mathrm{}$ and $g_e=1.8\mathrm{}$. The primary spectrum is due to recombination of an exciton strongly bound to the same center in a neutral state. Its magnetic splittings are explained by a strong-exchange model, with the singlet-exciton level 6.5 meV above the triplet level. The latter has a zero-field splitting of 0.2 meV, due to a preferred spin alignment along axial directions. A striking feature of the primary spectrum is the strong dependence of luminescence intensities on the direction of the magnetic field at 34 kG. A third charge state of the center is thought to be responsible for the slow quenching of several spectra under uv illumination. High-resolution measurements have resolved the axial-nonaxial pairs predicted by our model. Such pairs are resolved in each of the seven no-phonon doublets that are observed at 4.2 °K.