MOVPE growth and characterization of GaN/InGaN nanowires and microrods for next generation solid-state-lighting applications

A comprehensive study has been conducted in order to develop, understand and define the epitaxial growth process of InGaN/GaN nanowires (NW) and qualify their properties for application in future nanoLED devices. Vapor-liquid-solid (VLS) growth mode, selective area growth (SAG) and self-organized growth were investigated as three different approaches to create GaN rod structures. All of the grown samples were characterized by means of different complementary non-destructive techniques to analyze electrical and optical properties. In particular the QW emission was studied by microphotoluminescence (µPL), the crystal quality and strain through Raman scattering and the crystal structure by transmission electron microscopy (TEM). Some of the developed NWs were analyzed using advanced measurement set-up, in particular: nano-scale cathodoluminescence (CL) mapping or synchrotron-based characterization, including hard X-ray nanoprobe and X-ray fluorescence (XRF). The complex characterization allowed to understand the optical and structural properties of grown nanostructures and therefore helped to improve the growth process. Based on the obtained results, the development of selective area growth of GaN microrods on Si(111) substrates by MOCVD is discussed together with characterization and understanding of structural and optical properties of individual GaN rods. Additionally, the novel, innovative self-organized growth of GaN NWs on Si(111) is proposed as an alternative to the time consuming and expensive SAG method. The nano-scale characterization and understanding of structural and optical properties of newly developed InGaN/GaN NWs on silicon substrate are discussed providing the description of the current status of GaN NW on Si growth and the role of GaN rod on Si as the building block for the nanoLED.