High-resolution X-ray diffraction investigations of epitaxially grown ZnSe/GaAs layers

Abstract

Single-crystalline ZnSe layers were grown by metal-organic vapour phase and molecular beam epitaxy on (001) oriented GaAs substrates. The lattice mismatch between layer and substrate at growth temperature causes a strain in the layer material, which is relaxed by the nucleation of misfit dislocations. The relaxation process starts at the critical thickness, which depends on the growth conditions. The crystalline quality and the residual strain of the epilayers were investigated with a high-resolution X-ray diffractometer. Additionally, the intensity distribution of the scattered X-rays in the directions perpendicular and parallel to the reciprocal lattice vector (004) was observed by a two-reflection analyser crystal. For the system ZnSe/GaAs, this intensity distribution depends on the degree of strain relaxation, which is dependent on the layer thickness. The results are compared with transmission electron microscopy results.