Annealing-induced dislocation loops in Si-doped GaAs-AIAs superlattices

Abstract

Dislocation loops were observed to form in the Si-doped layer of an MBE-grown GaAs-AIAs superlattice structure as a result of annealing. The density and size of the loops, as estimated by cross-sectional TEM, were shown to depend on the As pressure, annealing time and temperature. The loops are proposed to nucleate as a result of the undersaturation of As vacancies, caused by the site-switching of Si atoms from group III sites to As sites. The deficient As vacancies are restored by the crystal which generates Frenkel pairs. Consequently, As interstitials are created in excess. These latter species precipitate in the form of platelets of interstitials which produce dislocation loops. As the annealing time increases and more excess interstitials are accommodated, the loops gradually dissociate by recombination of the interstitials forming the loops with vacancy pairs.