Optical and electrical properties of 4H-SiC epitaxial layer grown with HCl addition

The introduction of hydrogen chloride (HCl) in the deposition chamber during the growth of 4H-SiC epitaxial layers allows very high growth rates to be achieved. The properties of the epilayers and the growth rate depend on many parameters such as the growth temperature and the C/Si, Cl/Si, and Si/H-2 ratios. We have used optical and electrical measurements to investigate the effect of the Cl/Si and Si/H-2 ratio and growth temperature on the epitaxial growth process. The growth rate increases with increasing Si/H-2 ratio and higher growth rates are obtained when HCl is added to the gas flow. Optical microscopy shows an improvement of the surface morphology, and luminescence measurements reveal a decrease in the concentration of complex defects with increasing Cl/Si ratio in the range of 0.05-2.0 and with increasing growth temperature from 1550 degrees C to 1650 degrees C. The electrical measurements on the diodes realized on these epitaxial layers show a decrease of the leakage current with increasing Cl/Si ratio and growth temperature over the same range. Deep level transient spectroscopy measurements indicate that the deep level EH6/7, which is one of the main levels responsible for the high value of leakage current measured in the Schottky diodes, is greatly reduced using HCl as a growth additive.