Preparation And Properties Of Ce Doped GaN Nanostructures

Gallium nitride(GaN) is one important wide band-gap semiconductor applied in blue region devices, and GaN nanostructures have promising applications in the future nano-scaled optoelectronic devices. It is of great scientific and technological importance to tune the properties of GaN nanostructures by doping proper element. The thesis studied the growth and characterizations of Ce-doped GaN nanowires, and the following main results have been obtained.1. Ce-doped GaN nanowires were prepared by chemical vapor deposition(CVD) method assisted by Au catalyst using Gallium oxide and ceric oxide, or gallium and cerium chloride as the sources of Ga and Ce, and ammonia as the souce of nitrogen. The products were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), selected area electron diffraction(SAED), energy dispersive X-ray spectrometer(EDS), Raman spectroscopy and photoluminescence(PL). The results show that the samples synthesized from gallium oxide and ceric oxide are hexagonal wurtzite GaN single crystalline nanowires with uniform morphology. PL spectra of the samples show the near-band-gap emissions that have a slightly red shift with the increase of Ce contents. The samples synthesized using gallium and cerium chloride are also hexagonal wurtzite GaN single crystal nanowires but the morphology is not uniform. The near-band-gap emissions of the PL spectra of the samples have obviously red shifts and decrease of intensity with the increase of doping concentration. There is a new weak emission band appearing at 396.9nm.2. A two-step approach was proposed to achieve Ce doped GaN nanowires. Firstly, pure GaN nanowires were synthesized by chemical vapor deposition(CVD) method. Secondly, a solid-state sintering treatment was performed to obtain Ce-doped GaN nanowires by the diffusion of Ce ions into GaN nanowires. The products were characterized by XRD, SEM, TEM, HRTEM, SAED, EDS, XPS and PL. The results indicate that the samples are well-crystallized hexagonal wurtzite GaN single crystal nanowires. The longer duration of solid-state sintering would facilitate more Ce ions incorporated into the synthesized GaN nanowires with uniform distribution. PL spectra of the samples show the near-band-gap emissions with obviously red shifts that depend on the solid-state sintering duration.The thesis reports the preparation and characterizations Ce doped GaN single crystal nanowires through various techniques. There are some new results involed in the thesis, which would be helpful to the research of doped GaN nanowires with controlled properties.