Impacts of growth parameters on deep levels in n-type 4H-SiC

Deep levels in n-type 4H-SiC epilayers have been investigated by deep level transient spectroscopy. The Z1/2 and EH6/7 centers are dominant in epilayers grown with low C/Si ratios during chemical vapor deposition. By increasing the C/Si ratio, the Z1/2 and EH6/7 concentrations are decreased, while an unknown trap (the UT1 center, Ec−1.45 eV) is introduced. The Z1/2 and EH6/7 concentrations are not changed by increasing the growth rate from 14 to 23 μm/h at a fixed C/Si ratio. By increasing growth temperature from 1550 to 1750 °C, however, the Z1/2 and EH6/7 concentrations are significantly increased. From these results, the formation of Z1/2 and EH6/7 centers are mainly affected by the C/Si ratio and growth temperature rather than the growth rate. These phenomena can be explained with a model that both Z1/2 and EH6/7 centers are related to a carbon vacancy, which has been recently proposed by the authors.