Variations in the Measured Carrier Lifetimes of n^- 4H-SiC Epilayers

The effects of measurement technique and measurement conditions (injection level, temperature) on the measured carrier lifetimes in n- 4H-SiC epilayers are investigated. For three optical measurement techniques, it is shown that the high and low injection lifetimes can vary dramatically. Differences in the lifetime for varying injection level and temperature are approached both experimentally and via carrier dynamics simulations, assuming Z1/Z2 as the dominant defect. Reasonable agreement between measured and calculated behavior is obtained, as is insight into the recombination kinetics associated with the lifetime limiting defect.