Strain mapping in semiconductor nanowires using X-ray diffraction

Strain engineering in semiconductor materials facilitates the fabrication of novel electronic and optoelectronic devices. The electronic properties of semiconductors are determined by their building blocks, i.e. their atoms, and by the way how these building blocks are arranged, i.e. their crystal structure. If stress is applied, the spatial arrangement of the atoms is altered and the material is strained according to its mechanical response property, the stiffness. Within the elastic regime, strain results in a changed band structure of the material. The band structure of a semiconductor can be seen as a map of its electronic and optoelectronic properties. X-ray diffraction, being a versatile structural characterization method, probes the atom's electron clouds in crystalline materials, and is widely used to deduce the strain in semiconductor materials. In this work, X-ray diffraction is used to probe the strain distribution in semiconductor nanowires. Nanowires are several $\mu$m long rod shaped semiconductor structures with diameters below 100\,nm. Due to quantum confinement effects the nanowires are one-dimensional in terms of their electronic properties. This allows for the fabrication of various devices, being superior compared to similar state of the art devices. Standard ensemble X-ray diffraction experiments in connection with results from electron microscopy investigations were performed to investigate InAs/\InAsP\ nanowire heterostructures. These nanowire structures exhibit a strain state according to the material's lattice mismatch and the nanowire geometry.