Investigation of carrier lifetime behavior in the 4H-SiC homoepitaxial layer

The minority carrier recombination behavior of 4H-SiC epiwafer with epilayer thickness less than 15 $\mu$m has been investigated using time-resolved photoluminescence (TRPL) spectroscopy with a 266 nm laser source under low injection condition. A one-dimensional continuity equation was established to simulate the decay of excess carrier of epiwafer under the influence of surface recombination at both front and rear sides of the epilayer. Model simulations indicated that interface recombination velocity at epilayer/4H-SiC (S2) governs carrier decay after 1/e decay time when the surface recombination velocity at the front surface (S1) exceeds 1000 cm/s. By model fitting the measured carrier decay data of epiwafers with an epilayer bulk lifetime of 170 ns, S2 was determined to be $10^{3}$cm/s while the fitted S1 ranged from 2× $10^{4}$ to 4× $10^{4}$cm/s. S2 thus determined can be used as an index forjudging the quality of 4H-SiC wafer.