X‑ray Bragg Ptychography on a Single InGaN/GaN Core–Shell Nanowire
mediaposted on 2017-03-06, 00:00 authored by Dmitry Dzhigaev, Tomaš Stankevič, Zhaoxia Bi, Sergey Lazarev, Max Rose, Anatoly Shabalin, Juliane Reinhardt, Anders Mikkelsen, Lars Samuelson, Gerald Falkenberg, Robert Feidenhans’l, Ivan A. Vartanyants
The future of solid-state lighting can be potentially driven by applications of InGaN/GaN core–shell nanowires. These heterostructures provide the possibility for fine-tuning of functional properties by controlling a strain state between mismatched layers. We present a nondestructive study of a single 400 nm-thick InGaN/GaN core–shell nanowire using two-dimensional (2D) X-ray Bragg ptychography (XBP) with a nanofocused X-ray beam. The XBP reconstruction enabled the determination of a detailed three-dimensional (3D) distribution of the strain in the particular nanowire using a model based on finite element method. We observed the strain induced by the lattice mismatch between the GaN core and InGaN shell to be in the range from −0.1% to 0.15% for an In concentration of 30%. The maximum value of the strain component normal to the facets was concentrated at the transition region between the main part of the nanowire and the GaN tip. In addition, a variation in misfit strain relaxation between the axial growth and in-plane directions was revealed.