Depth resolved strainanalysis of lateral nanostrucutres by x-ray grazing incidence diffraction

Quantum well semiconductor heterostructures are increasingly important systems in the development of smaller, faster and more efficient electronic and optoelectronic devices. One way to modify the electronic band structure is to exploit quantum size effects requiring device engineering on a nanometer length scale. In particular, the lateral patterning of a strained stressor layer allows to achieve a lateral carrier confinement in a buried single quantum well as a result of the strain relaxation. The strain relaxation at free surfaces of the stressor layer induces a lateral inhomogeneous strain distribution and subsequently a lateral change of the optical properties within the single SQW. To exploit this effect in a device the structure has to be planarized by a second epitaxial step. The lateral carrier confinement of the initially free standing nanostructure can almost be maintained using a two step overgrowth process. The layout of the lateral nano structure (layer thicknesses and composition, shape) is predicted by finite element calculations of the strain distribution. The achieved optical properties are measured by photoluminescence; the strain field is probed by X-ray grazing-incidence diffraction.