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 ${\left|\nabla n\right|}^2$ 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 × ${10}^{-4\mathrm{}}$ erg/${\mathrm{cm}}^2$ and an electrostatic dipole barrier $\Delta \Phi$ of 0.16 meV. The small value of $\Delta \Phi$ leads to the conclusion that the charge on the droplet is negative.