Raman Investigation of Heavily Al Doped 4H-SiC Layers Grown by CVD

Abstract

In this work, we focus on heavily aluminum (Al) doped 4H-SiC samples. We compare the effect of the Al concentration and Hall carrier concentration on the Raman spectra in a large frequency range. The Al concentration measured by Secondary Ion Mass Spectrometry ranged from 2×1016 to 8.4×1019 cm-3 while the electrical measurement give a carrier concentration up to 5×1019 Al×cm-3. On the Raman spectra, three different frequency domains have been analysed: i) at high frequency where we consider the change in longitudinal optical phonon-plasmon coupled mode; ii°) at low frequency where we consider the continuum of electronic transitions and iii°) finally, considering the Fano interference effect between the continuum of electronic transitions and the Folded Transverse Acoustic phonon modes. This analysis is applied to comment a Raman spectra mapping collected on a 4H-SiC 2 inch wafer.