Competition of Radiation Processes in 6H-SiC Observed by Luminescence

We report on the results of photoluminescence and thermoluminescence measurements of various 6H-SiC crystals. At low temperature in all n-type samples two bands with maxima at 2.7 eV (blue) and 1.8 eV (orange) were detected. In the p-type material only blue band was observed. The measurements performed at a broad range of temperatures showed totally different behaviour of photoluminescence intensity of both bands. The presented results could be explained in the model assuming well established donor-acceptor pair recombination for the blue band emission and the conduction band - deep defect transition for the orange band. The proposed model was confirmed by thermoluminescence measurements of the orange band which showed peaks at 30 K, 80 K, 100 K, 150 K attributed to ionization of subsequent shallow donor levels.