STUDY OF MICRODEFECTS IN GAAS BY X-RAY DIFFUSE-SCATTERING

Microdefects have been studied by X-ray diffuse scattering in Si-doped, In-doped and undoped GaAs single crystals grown by the liquid encapsulated Czochralski method. The X-ray measurements have been performed with a high resolution diffractometer equipped with a four reflection Ge monochromator, using the Cu Ka radiation and the 004 symmetric reflection; a nearly perfect Ge crystal has been used as the reference specimen for measuring the thermal diffuse scattering. In the Si-doped crystal evidence for the presence of clusters of interstitial point defects has been obtained. In the other samples the measurements indicate the presence of extrinsic dislocation loops. As far as the undoped samples are concerned, the intensity of the extra scattering increases by increasing the stoichiometric ratio and the dislocation density. It may be argued that the loops probably originate by the aggregation of As interstitials and are associated with the dislocations.