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 reflect ion are applied for spatial and temporal characterization of 6H-SiC. T wo different substrate crystals grown by the Lely method and a 5 mu m thick layer grown by liquid phase epitaxy are tested. High spatial res olution time-resolved measurements reveal a significant variation of t he effective carrier lifetime on a nanosecond time scale, related to t he random distribution of crystal imperfections. Second harmonic gener ation (SHG) in reflection measurements reveals pronounced structural a nd crystalline quality differences of the tested samples. The roles of nonequilibrium carrier radiative, nonradiative, and enhanced surface recombination processes are discussed on the basis of the experimental data.