Spatial distribution of electron-hole droplets in silicon

We report the first determination of the electron-hole liquid-distribution resulting from point laser excitation of Si. A cloud is observed with volume increasing nearly linearly with laser power, resulting in an almost constant average pair density. The cloud is slightly anisotropic in shape and is most dense at a point well within the crystal. The average pair density in the cloud is found to be 0.5% of the spectroscopically determined density of the liquid phase, nₑₕ=3.3×10¹⁸ cm^-3. The low average density indicates that the luminescence distribution is due to a diffuse cloud of discrete droplets which occupy a small fraction of the total cloud volume. The size and density characteristics of the cloud are consistent with earlier phonon-wind models for Ge, which propose a nonequilibrium phonon flux as the dominant droplet-transport mechanism.