The material quality of CVD-grown SiC using different carbon precursors

We report an investigation where nine different hydrocarbons have been used as carbon precursor in the growth of 4H and 6H silicon carbide (SiC) epitaxial layers. For the various growths the C/Si ratio was varied from 2 to 6, the temperature in the range 1550-1600 degrees C, and the growth rate was about 3-4.6 mu m/h. All hydrocarbons, except methane, could be used for growth of high crystal qualify epitaxial layers at low C/Si ratio and low growth rate (3 mu m/h) as confirmed by the smooth morphology, and by low-temperature photoluminescence showing strong free exciton and narrow well-resolved nitrogen-bound exciton lines. Hydrogen-related lines could be observed in the spectra of epitaxial layers grown with C-precursors which have double and triple bonds in the molecule. The unintentional incorporation of p-type dopants, such as, aluminium and boron impurities is proposed to correlate to the surface roughness. Propane gave the most stable growth of the hydrocarbons as C-precursor at higher growth rate.