Magneto-Optical Properties and Recombination Rate of the Green Luminescence in Cubic SiC

The Zeeman effect of the recombination radiation from a shallow bound exciton in cubic SiC has been studied at 1.6 °K as a function of magnetic field strength and direction. The observed pattern of the Zeeman-split lines is consistent with the Zeeman splitting expected from an exciton bound to a neutral donor, in which the ground state has a singlet electron bound to the donor and the excited state has two paired electrons in addition to a $j=\frac{3}{2}$ hole. This is consistent with a model for this transition proposed by Choyke et al. The measured polarizations, relative intensities, and thermalization of the split lines are also consistent with the theory for an exciton bound to a neutral donor. The measured $g$ values are $g_e=1.\mathrm{}96\pm 0.06$; $g_{h_{\frac{1}{2}}}=1.\mathrm{}12\pm 0.03$; $g_{h_{\frac{3}{2}}}=1.\mathrm{}10\pm 0.03$. No angular anisotropy was observed in the pattern of the Zeeman lines, in agreement with the theoretical angular dependence of the splittings calculated with the experimental $g$ values for a point defect which is a neutral donor. The no-phonon line is split into two components under uniaxial stress $\parallel 〈110〉$, consistent with the description of the donor energy states given above. A hydrostatic-pressure deformation-potential constant $a=-2.\mathrm{}2\pm 0.3$ eV was obtained. Satellites of the principal green bound-exciton lines are identified with transitions from excited states by a comparison of spectra at 1.6 and 20.6 °K in different crystals. The low photoluminescence efficiency of the green emission, and the short decay time obtained from a pulsed photomuminescence experiment, suggest that an Auger process dominates the recombination, as expected for an exciton bound to a neutral donor in an indirect gap semiconductor such as SiC.