Structural and cathodoluminescence properties of gallium nitride nanorods by HVPE

Single crystalline GaN nanorods are formed on a sapphire substrate by hydride vapor phase epitaxy (HVPE). Their structural and optical properties are investigated by x-ray diffraction scanning and transmission electron microscopy, and cathodoluminesence (CL) techniques. A high density of straight and well-aligned nanorods with a diameter of 80-120 nm formed uniformly over the entire 2 inch sapphire substrate. The x-ray diffraction patterns and transmission electron microscopic images indicate that the formed GaN nanorods arc pure single crystals and preferentially oriented in the c-axis direction. We observed a higher CL peak position of individual GaN nanorods than that of bulk GaN as well as a blueshift of CL peak position with decreasing diameter of GaN nanorods, which are attributed to a quantum confinement effect in one-dimensional GaN nanorods. We demonstrate that well-aligned, single crystalline GaN nanorods with high density, high crystal quality, and good spatial uniformity are formed by the HVPE method.