X-RAY DIFFUSE-SCATTERING IDENTIFICATION OF MATRIX AS-RICH MICRODEFECTS IN GAAS CRYSTALS

Microdefects related to the small etch pit background in LEC and HB GaAs crystals undoped and doped with Si, Te, In and Zn were studied by triple-crystal diffractometer measurements of X-ray diffuse scattering and selective etching. The microdefects related to these nondislocative etch pits have never been revealed by TEM, in spite of their high density. The similarity of the X-ray diffuse scattering features in all the samples characterized by such an etch pattern makes it evident that all these crystals contain a high density of microdefects of the same crystallographic nature that can be considered as As self-interstitial aggregates having a nucleus of a finite size and long-range diffuse boundary with the GaAs matrix. The density and size of these microdefects varied from 10(7) to 10(11) cm-3 and from 0.1 to 0.5-mu-m, respectively. The computer simulation of the diffuse scattering associated with different crystallographic types of defects showed that the microdefects observed are {113}-planar interstitial aggregates surrounded by the extended atmospheres of native point defects and/or impurities.