Importance of many-body effects in the clustering of charged Zn dopant atoms in GaAs

The spatial distribution of negatively charged Zn dopant atoms in GaAs has been investigated by cross-sectional scanning tunneling microscopy. At high densities, the dopant atoms exhibit clear clustering behavior, suggesting the existence of an effective attractive interaction in addition to the scr eened Coulomb repulsion between two dopants. By analyzing the data through Monte Carlo simulations, we have extracted the intrinsic screening length a t different dopant densities and attributed the origin of the effective att raction to strong many-body effects in the dopant-dopant repulsion.