Structural and Optical Properties of Disc-in-Wire InGaN/GaN LEDs
Scott A. Wight, Babak Nikoobakht
This study aims to examine the role of the microstructure and optical properties of InGaN/GaN nanowire LED structures on Si (111) having different nanowire densities. Cathodoluminescence measurements show that all samples exhibit broad emission around the intended 635nm wavelength. The emission intensity of each sample varies due to a competition between the formation of coalescence defects, which tends to decrease the overall emission intensity, and the absolute number of emitting nanowires, which tends to increase the overall emission intensity. The width of the emission peak is likely due to variations in the morphology of the InGaN within the wires, as faceted layers with different thicknesses and quantum dots are observed by Transmission Electron Microscopy. Non-epitaxial 6-fold symmetric lateral branching, called "nanocrowns," emanate from stacking faults within the active regions. These features quench optical emission as a result of multiple grain boundaries between the nanocrown and nanowire.