Motion of Electron-Hole Drops in Pure Ge

We study the motion of electron-hole drops in pure Ge at 2°K. An analysis of their luminescence by a time- and space-resolved technique yields their diffusion coefficient (150 ${\mathrm{cm}}^2$ / sec) and their lifetime (40 μsec). We also measure the formation time (0.1-0.7 μsec) of drops containing about ${10}^6$ electron-hole pairs. A discussion of these new results is given.