Diffusion of Zinc in Gallium Arsenide

Abstract

ZINC is an acceptor impurity in gallium arsenide with small ionization energy. If it is the predominant impurity and is present in low enough concentration, then the Fermi-level will lie above the zinc-levels and the zinc atoms will nearly all be ionized, that is, they will have accepted an electron. As the zinc concentration increases, the Fermi-level will descend into the valence band and the proportion of ionized atoms becomes small. Since the speed of diffusion of an atom will be different in its ionized and in its un-ionized state the diffusion coefficient will depend upon concentration.