On the investigation of the diffusion processes of photoexcited carriers in silicon by ps-reflectivity measurements

Abstract

The optical excitation of non-equilibrium charge carriers in semiconductors results in a carrier distribution which gives rise to a diffusion process into the bulk of the semiconductor. The diffusion time depends on the absorption coefficient and on the ambipolar diffusion constant. These diffusion times are on a subnanosecond time scale for our experimental conditions. By time-resolved reflectivity measurements we have studied the dependence of the ambipolar diffusion constant on the density of excited carriers. Experimental results were compared with theoretical ones.