Self-consistent calculation of surface properties of electron-hole droplets

The surface energy of the electron-hole liquid in Ge is calculated using the density-functional formalism. The kinetic energy is included exactly within an uncoupled spherical band model. Corrections to order |∇n|² are included in the evaluation of the exchange and correlation energy and also in the evaluation of the effects of band coupling and anisotropy on the kinetic energy. We obtain a surface energy of 2.5 ×{} 10^-4 erg/cm² and an electrostatic dipole barrier ΔΦ of 0.16 meV. The small value of ΔΦ leads to the conclusion that the charge on the droplet is negative.