Nonlinear screening of positive and negative point charges in GaAs

Abstract

We have used a variational approach for approximately solving Resta's nonlinear Thomas-Fermi equation for the potential of (point) charges in GaAs. We have considered the cases of charges (in atomic units) Z = ±0.16, ±1.16, ±0.84. The charges Z = +0.16 and Z = −0.16 are the effective charges due to the partial ionicity of the chemical bonds on a Ga and As site, respectively. The charge Z = +0.84 corresponds to a Column VI donor on an As site, that of Z = +1.16 to a Column IV donor on a Ga site. Similarly, the charge of Z = −1.16 corresponds to a Column IV acceptor on an As site, that of Z = −0.84 to a Column II acceptor on a Ga site. As a result of our calculations, we have obtained site-dependent and charge-dependent spatial dielectric functions that describe the screening of the (point) charges by the valence electrons of (pure) GaAs.