Crystal Structures and Surface Plasmon Properties of GaZnO Nanostructures

In this paper, we show the crystal structures of MBE-grown highly Ga-doped ZnO (GaZnO) nanowires and the optical properties of a GaZnO nano-grating. In particular, we demonstrate the morphology difference between the GaZnO nanowires grown with the vapor-liquid-solid mode under the Zn- and O-rich growth conditions by using Ag nanoparticle as growth catalyst. Also, we illustrate the polarity difference between the nanowires grown under these two conditions and interpret the mechanisms behind this difference. It is found that under the Zn-(O-) rich growth condition, the polarity of GaZnO nanowires is always Zn- (O-) polar no matter which polarity of the used GaN substrate is. This behavior is attributed to the faster lateral growth of GaZnO with the vapor-liquid-solid mode in the Zn- (O-) polar structure under the Zn- (O-) rich growth condition. Meanwhile, by fabricating a GaZnO nano-grating structure, we observe the surface plasmon resonance behavior at the GaZnO/air interface in the wavelength range of 1400–1700 nm. The surface plasmon resonance behavior is confirmed by the measurement of its dielectric constant and numerical simulations on the electromagnetic scattering/absorption properties. Such surface plasmon resonance behavior can be applied to a Si solar cell for enhancing sunlight harvest.