This paper presents the results of studies of the photoluminescence intensity distribution in various sections of the surface of epitaxial layers of gallium arsenide grown on silicon substrates. It is established that the epitaxial layers have a block structure in the form of radiative areas separated by dark (nonradiative) boundaries, whose shape depends on the substrate's crystallographic orientation. It is assumed that the block structure is associated with internal stresses that arise in the epitaxial layers because of differences of the lattice constants and thermal expansion coefficients of the connected materials.
Yu. S. Emel'yanenko and F. M. Katsapov, "Features of the photoluminescence of epitaxial layers of GaAs grown from the vapor phase on silicon substrates," J. Opt. Technol. 70, 713-714 (2003)