Annealing studies of B+ implanted 6H-SiC by RBS and optical sub-gap spectroscopy

B+ ions were implanted into 6H-SiC at room temperature and annealing was performed in nitrogen ambient at temperatures up to 450 degrees C or 1000 degrees C. The layers were analyzed by Rutherford backscattering-channeling spectrometry and sup-gap optical spectroscopy yielding the depth and the spectral dependence of the absorption coefficient and the refractive index, In the case of a very low defect concentration obtained by implantation of 7 x 10(13) B(+)cm(-2) a temperature of 1000 degrees C is necessary to remove the absorbing point defects and point defect complexes. The annealing of an amorphous SIC layer (ion dose 1 x 10(16) B(+)cm(-2)) at temperatures between 300 degrees C and 450 degrees C is connected with an increase of the optical gap energy (i.e. with a decrease of the absorption coefficient), and with a decrease of the refractive index and of the swelling of the layer, These effects seem to be connected with the relaxation of the amorphous network. A SiC layer of an intermediate defect state was obtained after implantation of 2 x 10(15) B(+)cm(-2). The results indicate that this layer contains amorphized SiC regions surrounded by weakly damaged crystalline SiC, From the analysis of the optical spectra it can be concluded that already after annealing at temperatures up to 400 degrees C the amount of amorphous SIC decreases remarkably.