ANALYSIS OF LARGE IMPURITY ATMOSPHERES AT DISLOCATIONS AND ASSOCIATEDPOINT-DEFECT REACTIONS IN DIFFERENTLY N-DOPED GAAS CRYSTALS

The large impurity atmospheres at dislocations typical of n-type (Si- or Te-doped) GaAs crystals have been analysed by localized measurement s of the free electron concentration, diffusion length and DSL etching velocity. The atmospheres always contain dopant atoms as well as poin t defects (complexes) whose formation and type depend on the type of d opant impurity and melt stoichiometry. The donor- or acceptor-like cha racteristics of such point defects (complexes) are responsible for the observed remarkable difference in the electrical and recombinative pr operties of the atmospheres between the differently doped crystals. Th e point defect reactions at the base of the formation of the slip trac es are discussed. The possible mechanisms of the impurity-dislocation interaction leading to the formation of the atmospheres are also consi dered.