Defect structure of InAlAs/InP layers

In x Al 1 − x As layers on InP substrate can be subjected to compressive as well as tensile strain due to lattice parameter differences induced by suitable alloy composition changes. The 2 μm thick In x Al 1 − x As (0.50 ≤ x ≤ 0.53) layers were grown on the (0 0 1) oriented InP substrates by molecular beam epitaxy (MBE). They were investigated using X-ray diffraction and chemical etching. X-ray studies were performed applying high-resolution diffractometry in the double (DAD) and triple (TAD) axis configuration. It was found that the In 0.53Al 0.47As/InP layer under compressive strain relaxes partially along two 〈1 1 0〉 directions. On the other hand, the In 0.50Al 0.50As/InP layers, being under tensile strain, consist of two sub-layers; the first one, adjacent to the substrate is pseudomorphic whereas the upper sub-layer is partially relaxed and the relaxation is anisotropic. The upper sub-layer is fully strained in the [1 1 0] direction while partially relaxed in the [−1 1 0] one.