Laser Doppler Velocimetry of Electron-Hole Drops in Germanium

Abstract

We report the first direct measurement of velocity distributions of electron-hole drops, and discuss them in relation to existing theoretical models. The data, obtained by frequency analysis of scattered light, show acceleration near the surface, while at larger depths, the drops appear to experience viscous deceleration with a relaxation time of ${10}^{-4\mathrm{}}$ sec. We find difficulties in reconciling the data with the present ideas of forces resulting from excitons, phonons, or mutual repulsion.