Evolution of deep defect centers in semi-insulating 4H-SiC substrates under high-temperature annealing

The influence of postgrowth high-temperature anneals between 1400°C and 2400°C on the behavior of the D ₁ center in semi-insulating 4H-SiC was studied by photoluminescence. The optical signature of D ₁ was observed up to 2400°C with intensity maxima at 1700°C and 2200°C. It was also found that changes in the postannealing cooling rate drastically influence the behavior of the D ₁ center and the concentrations of the V _C, V _Si, V _C-V _Si, and V _C-C _Si lattice defects observed from electron paramagnetic resonance experiments. The change in intensity of the D ₁ defect has some correlation with the intensity change of the V _C-V _Si pair defect at temperatures above 1900°C. In addition, infrared photoluminescence spectroscopy studies showed that changes in the intensity of the D ₁ defect at 2100°C to 2400°C annealing temperatures and variable cool-down rates have close correlation with intensity changes of the UD2 defect.