Behavior of native defects in semi-insulating 4H-SiC after high temperature anneals and different cool-down rates

We have recently explored the nature and stability of native defects in high-purity semi-insulating 4H-SiC bulk substrates grown by PVT and HTCVD methods after post-growth anneal treatments up to 2400°C using electron paramagnetic resonance (EPR) and low-temperature photoluminescence (PL) experiments. In the present study we have extended these investigations to SI 4H-SiC subjected to the same post-growth high-temperature anneal treatments, where significantly enhanced carrier lifetimes have been reported for such conditions, but cooled at different rates ranging from ∼2-25°C/min. Previously, the intensities of the native defects decreased monotonically with anneals from 1200-1800°C; however, it was recently observed that several of these defects reappear after annealing at 2100°C and above. Our results illustrate the effects of the post-growth anneal treatments and cool-down rates on the concentrations of native defects.