Structural ordering involving impurities in multilayer homoepitaxial structures subjected to low radiation doses

Electrophysical, photoelectric, electrooptic, and metallographic techniques are used to study radiation ordering in n(+)-n-n(++) GaAs multilayer homoepitaxial structures with metal contacts (Au, Sn, Cr, Pt). This ordering, which shows up as increased carrier mobility and lifetime, results from a decrease in the rate of nonradiative recombination, is most pronounced in thin n(+)-type surface layers, and occurs only in structurally imperfect materials with a high concentration of three-dimensional defects (domes). The experimental features of the radiation ordering effect indicate that penetrating radiation induces structural and impurity changes in the n(+)-type GaAs surface layer. It is suggested that the interaction between impurities and primary defects leads to the formation of neutral complexes. The enhancement of the ordering effect at the surface is attributed to planar gettering of defects during which the defects move along the surface. 19 references