Excitation wavelength-dependent carrier dynamics in n-type and semi-insulating 6H-SiC using ultrafast transient absorption spectroscopy

摘要

Transient absorption spectroscopy was utilized to monitor ultrafast carrier dynamics in conductive and semi-insulating 6H-SiC wafers. By tuning the excitation wavelength around the bandgap of 6H-SiC (365-400nm), the surface and bulk recombination processes could be accordingly distinguished. Simultaneously, the locations of surface and defect states in the bandgap were inferred by investigating the evolution of transient absorption spectra for different photoexcited carrier distributions. Vanadium (V) doping had a notable modulation on transient absorption in semi-insulating 6H-SiC, resulting from an additional decay process induced by carrier capturing of V deep levels. The carrier lifetimes induced by various recombination mechanisms were determined and interpreted unequivocally by global analysis and simplified model. The time constant via bulk capturing (approximate to 400ps) was three orders of magnitude faster than that via inherent defects. Controlling the lifetime by excitation wavelength and doping conditions is essential for fabricating 6H-SiC-based ultrafast photonic devices.%235703.1-235703.9