X-ray excited optical luminescence imaging of InGaN nano-LEDs

In this work, an imaging tool to investigate optical inhomogeneities with site and chemical sensitivities has been integrated in a synchrotron radiation nanoprobe. Coaxial GaN/In _1-xGa _xN/GaN/ZnO nanoarchitecture light emitting diode (LED) arrays are used to validate the scanning x-ray excited luminescence technique. Elemental maps and luminescence images of the hexagonal InGaN multiple quantum wells and inner deposited layers are reported with 120 nm spatial resolution. Within the experimental accuracy, the X-ray fluorescence results reveal an homogeneous distribution of the major elements involved in the pattern formation and heteroepitaxial nanotube growth. In comparison to the morphological pattern, the optical emissions from individual nanowires exhibit a striking spatial variation, indicating significant changes in the quantum confinement effects.