Formation Mechanisms of InGaAs Nanowires Produced by a Solid-Source Two-Step Chemical Vapor Deposition

The morphologies and microstructures of Au-catalyzed InGaAs nanowires (NWs) prepared by a two-step solid-source chemical vapor deposition (CVD) method were systematically investigated using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The detailed structural characterization and statistical analysis reveal that two specific morphologies are dominant in InGaAs NWs, a zigzag surface morphology and a smooth surface morphology. The zigzag morphology results from the periodic existence of twining structures, and the smooth morphology results from a lack of twining structures. HRTEM images and energy-dispersive X-ray spectroscopy (EDX) indicate that the catalyst heads have two structures, Au₄In and AuIn₂, which produce InGaAs NWs in a cubic phase crystalline form. The growth mechanism of the InGaAs NWs begins with Au nanoparticles melting into small spheres. In atoms are diffused into the Au spheres to form an Au-In alloy. When the concentration of In inside the alloy reaches its saturation point, the In precipitate reacts with Ga and As atoms to form InGaAs at the interface between the catalyst and substrate. Once the InGaAs compound forms, additional precipitation and reactions only occur at the interface of the InGaAs and the catalyst. These results provide a fundamental understanding of the InGaAs NW growth process which is critical to the formation of high-quality InGaAs NWs for various device applications.