On the Formation of Intrinsic Defects in 4H-SiC by High Temperature Annealing Steps

In this paper the impact of high temperature annealing on the formation of intrinsic defects in 4H-SiC such as Z1/2 and EH6/7 was examined. Therefore, three epitaxial layers with various initial concentrations of the Z1/2- and EH6/7-centers (1011 – 1013 cm-3) were investigated. It turns out that depending on the initial defect concentration the high temperature annealing leads to a monotone increase of the Z1/2- and EH6/7-concentration in a temperature range from 1600 to 1750°C. For a defined temperature above these values, the resulting defect concentration is independent of the sample’s initial values. Beside the growth conditions themselves such as C/Si ratio the thermal post-growth processing has a severe impact on the carrier lifetime which must be taken into account during device fabrication.