Investigation of carrier lifetime in 4H-SiC epilayers and lifetime control by electron irradiation

Carrier lifetimes in $4H\text{-}\mathrm{Si}\mathrm{C}$ epilayers are investigated by differential microwave photoconductivity decay measurements. When the $Z_{1∕2}$ concentration is higher than ${10}^{13}{\mathrm{cm}}^{-3}$ , the $Z_{1∕2}$ center works as a recombination center. In this case, carrier lifetimes show positive dependence on the injection level (number of irradiated photons). On the other hand, other recombination processes such as surface recombination limit the lifetime when the $Z_{1∕2}$ concentration is lower than ${10}^{13}{\mathrm{cm}}^{-3}$ . In this case, carrier lifetimes have decreased by increasing the injection level. By controlling the $Z_{1∕2}$ concentration by low-energy electron irradiation, the lifetime control has been achieved.