Carrier lifetime variation in thick 4H-SiC epilayers using two-photon absorption

Carrier lifetime control in thick silicon carbide (SiC) epilayers is essential for fabricating >10 kV devices. Lifetime depth profiles were investigated in n-type and p-type SiC epilayers using photoluminescence (PL) decay excited by two-photon absorption (TPA), using 586 nm laser pulses. TPA limits the excitation to a small volume, and the observed PL decays exhibit nonexponential behavior resulting from the three-dimensional carrier diffusion occurring during the decay. The results were analyzed using a formalism that includes the effects of carrier lifetime, carrier diffusion, and surface recombination on the PL decay. The lifetime depth profiles exhibited a nonuniform lifetime-degrading defect concentration within the epilayers.