Ferromagnetic Cu-doped GaN film was grown on a GaN-buffered sapphire (0001) substrate by a hybrid physical-chemical-vapor-deposition method (HPCVD). The GaCuN film (Cu: 3.6 at.%) has a highly c-axis-oriented hexagonal wurtzite crystal structure, which is similar to GaN buffer but without any secondary phases such as metallic Cu, CuxNy, and CuxGay compounds. Two weak near-band edge (NBE) emissions at 3.38 eV and donor-acceptor-pair (DAP) transition at 3.2 eV with a typical strong broad yellow emission were observed in photoluminescence spectra for GaN buffer. In contrast, the yellow emission was completely quenched in GaCuN film because Ga vacancies causing the observed yellow emission in undoped GaN were substituted by Cu atoms. In addition, GaCuN film exhibits a blue shift of NBE emission, which could be explained with the +2 oxidation state of Cu ions, replacing +3 Ga ions resulting in band gap increment. The valance sate of Cu in GaCuN film was also confirmed by x-ray photoelectron spectroscopy (XPS) analysis. The GaCuN film shows ferromagnetic ordering and possesses a residual magnetization of 0.12 emu/cm3 and a coercive field of 264 Oe at room temperature. The unpaired spins in Cu2+ ions (d9) are most likely to be responsible for the observed ferromagnetism in GaCuN.

The growth of ZnO film on (0001) sapphire substrates was studied using the high density helicon wave oxygen plasma (>1011/cm2) assisted evaporation process. The addition of Ar into oxygen plasma (Ar/O2=1/2) enhanced the production of excited atomic oxygen (O*). The effect of a grounded grid installed at the exit of the plasma source on the crystallinity and optical properties of film is discussed. The full width at half maximum (FWHM) of θ rocking curve for (0002) plane is 0.53° under grid installation while 0.63° without the grid, indicating slightly improved crystallinity when adopting a grounded grid. The AFM image for the film deposited with grid installation shows a smoother surface morphology than in the case of no grid. PL spectra for the film deposited with the aid of a grid show a strong near-band edge emission at 3.36 eV at 10K, but those without a grid show prominent deep-level emissions. The deep level emission is attributed to the impurities and native defects in the film. The optical properties were greatly improved by a grounded grid, which effectively eliminated the ionic species and selectively extracted the excited neutrals.

The epitaxial layers of AIN and GaN were grown on Si and Sapphire substrate at a relatively low temperature of around 500 °C using the process of reactive ion beam assisted deposition. The optimum ion beam energy for epitaxial growth of AIN and GaN films was found to be about 50 eV. Characterization of the epitaxial layers was carried out by GID (Grazing-Incidence x-ray Diffraction) and high resolution TEM observation. The orientational relations between epitaxial layer and substrate were determined through these analysis. Very thin amorphous layers were observed at the interfaces of bom AIN and GaN films grown on Si(111) substrate, whereas the films grown on Sapphire substrate has no amorphous layer. The amorphous layer may act as a buffer layer enabling the growth of the epitaxial layers of AIN and GaN by relaxing the misfit strain in the early growing stage.