Control of composition and morphology in InGaAs nanowires grown by metalorganic vapor phase epitaxy

InGaAs nanowires grown by Metalorganic Vapor Phase Epitaxy (MOVPE) are promising candidates in future device technologies. The control of the chemical composition of InGaAs nanowires is not trivial due to the In atom diffusion from the substrate, which causes significant variations in the chemical composition along the nanowire. In this work, we report on the growth of InGaAs nanowires on (111)B InAs substrates followed by the characterization using high-resolution x-ray diffraction (HRXRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) as well as scanning transmission electron microscopy (STEM) in combination with energy dispersive X-ray spectroscopy (EDS). By detailed analyses of the HRXRD spectra and their variations with nanowires grown for different times, fundamental insight was gained into tapering formation and chemical composition gradient of the nanowires. The measurements show that acceptable uniformity of In and Ga concentrations along InGaAs nanowires can be achieved, and the maximum achievable nanowire length without tapering depends on the nanowire density. Finally, by carefully choosing the growth conditions, the morphology of the InGaAs nanowire can be further optimized.