Temporal and spatial investigation of 6 H-SiC by picosecond pulse excitation

Sensitive linear and nonlinear optical methods of picosecond transient reflectivity, fluorescence, and second harmonic generation in reflection are applied for spatial and temporal characterization of 6 H-SiC. Two different substrate crystals grown by the Lely method and a 5 μm thick layer grown by liquid phase epitaxy are tested. High spatial resolution time-resolved measurements reveal a significant variation of the effective carrier lifetime on a nanosecond time scale, related to the random distribution of crystal imperfections. Second harmonic generation (SHG) in reflection measurements reveals pronounced structural and crystalline quality differences of the tested samples. The roles of non-equilibrium carrier radiative, nonradiative, and enhanced surface recombination processes are discussed on the basis of the experimental data.