Papers by Author: M. Sūdžius

Abstract: We applied picosecond four-wave mixing technique to investigate carrier diffusion and recombination in n-type 4H-SiC epilayers. The dependence of bipolar diffusion coefficient D on photocarrier density was measured in range from ~ 1017 to ~ 1020 cm-3. We determined a decrease of D value from 3.4 to 2.2 cm2/s with increase of the photoexcitation level in range from ~ 1017 to ~ 1019 cm-3, and found its increase up to 3.8 cm2/s at carrier density above 1020 cm-3. Auger recombination governed decrease of carrier lifetime from 11 ns at ~ 1017 cm-3 to 1.8 ns at ~ 1020 cm- 3 has also been observed.

Abstract: We applied four-wave mixing (FWM) technique for investigation of high temperaturechemical vapour deposition (HTCVD) grown 4H-SiC samples with different doping levels. The determined minority electron and hole mobilities in heavily doped crystals at doping densities of 1019 cm-3 were found to be equal to 116 and 52 cm2/Vs. In semi-insulating (SI) crystals, the ambipolar diffusion coefficient Da = 2.6 − 3.3 cm2/s and carrier lifetimes of 1.5 – 2.5 ns have been measured. Irradiation of SI crystals by 6 MeV electrons resulted in essential decrease of carrier lifetime down to ~ 100 ps and clearly revealed the defect-assisted carrier generation with respect to two-photon interband transitions before irradiation.