Abstract
A local density functional cluster method is used to investigate the structure of dislocations in GaAs as well as their interaction with impurities. We find the 90° Ga(g) (β) partial is strongly reconstructed in the same way as in Si, but the As(g) (α) partial is not. This can account for the higher mobility observed for As(g) partials over Ga(g) ones. The influence of impurities on these core structures are discussed.