Anisotropy in the Shape of the Electron-Hole-Droplet Cloud in Germanium

Abstract

Using a special infrared scanning technique we have produced photographs of the electron-hole-droplet cloud in unstressed Ge. Contrary to past beliefs, the cloud of droplets resulting from focused-laser surface excitation in neither spherical, hemispherical, nor cylindrically symmetric about the excitation point. The observed concentration of droplets along certain crystal-symmetry axes provides compelling evidence for a phonon wind which pushes droplets into the sample.