Confocal micro-Raman characterization of SiC epilayers

The large visible optical penetration depth makes it difficult to isolate the Raman signals of SiC epilayers from those of the substrates such as SiC, sapphire and Si when visible laser lines are used. In this work, confocal micro-Raman was used to characterize 3C, 4H and 6H SiC layers on different substrates with enhanced lateral resolution (similar to 0.8 mu m) and depth resolution (similar to 2 mu m). Both lateral and depth variation of the free electron concentration and scattering time were measured from n(-) SiC epi layers on n(+) SiC substrates and from H+ implanted SiC. A defect mode induced by oxidation process was also analyzed as function of the depth and the lateral position.