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Abstract: We have grown Fe3N films on GaN(0002) substrates by metalorganic chemical vapor deposition (MOCVD). Under lower growth temperatures, small iron particles were formed on GaN surface, while under higher growth temperatures, Fe3N films were formed. The surface morphology of samples with different growth temperatures were characterized by atomic force microscopy. In X-ray Photoelectron Spectroscopy (XPS) measurement, the coexistence of metallic Fe and Fe2+ or Fe3+ was observed in the sample grown at 600°C, while the sample grown at 1050°C showed only high valence forms of Fe ions. It was also found that the magnetic moments of Fe3N prefer to align normal to the c-axis. [Copyright &y& Elsevier]

Abstract: The alloy Al x Ga1− x N was grown by metal-organic chemical vapor deposition (MOCVD) using a high-temperature AlN interlayer on a thick GaN template. The Al composition (x) of the Al x Ga1− x N was varied in the range 0.13⩽x⩽0.8. The in-situ reflectance spectra indicate that the growth process of AlGaN alloys is dominated by trimethylgallium (TMGa) molar flux when the molar flux of trimethylaluminium (TMAl) is kept constant. The Al compositions and growth rates of AlGaN alloys were determined by Rutherford backscattering, which indicates that the incorporation efficiency of TMAl is improved remarkably by decreasing the TMGa molar flux. The crystalline quality of these AlGaN alloys is evaluated by measuring the symmetric (002) and asymmetric (102) ω-scan X-ray diffraction peak widths. The best crystalline quality, among these Al x Ga1− x N alloys, is for an Al composition of x=0.54 where the full-width at half-maximums of the AlGaN (002) and (102) diffraction peaks are 265 and 797arcsec, respectively. This conclusion is consistent with the surface morphology of the AlGaN alloys probed by atomic force microscopy. Room temperature cathodoluminescence spectra show pronounced near band edge emission from these AlGaN alloys. The optical band gaps (E g) are found to deviate from linear interpolation between E g GaN and E g AlN with a bowing parameter b=0.89. [Copyright &y& Elsevier]

Abstract: AlN/Al0.3Ga0.7N distributed Bragg reflectors (DBRs) are grown on sapphire (0001) by metal-organic chemical vapor deposition (MOCVD). The number of stacks of the DBRs varies between 6 and 30. The thickness of the quarter-wave layers is designed such that the target peak reflectance locating at the wavelength of 330nm. The GaN or AlGaN templates are employed for growing the AlN/AlGaN DBRs. It is found that the templates intensively influence on the surface roughness and the interfacial properties of AlN/AlGaN DBRs. The result of atomic force microscopy indicates that the AlN/AlGaN DBRs grow on GaN template under quasi-two-dimensional mode. And the good interfaces of AlN/AlGaN not only clearly observed by cross-sectional scanning electron microscopy, but also concluded from narrow width and high orders of satellite peaks detected by high-resolution X-ray diffraction. The peak reflectance of 20 stacks DBRs on GaN template reaches up to 82% located at 326nm.While those DBRs grown on AlGaN template do not show such structural and optical properties due to the rough surface of AlGaN template and the poor interfaces of AlN/AlGaN. [Copyright &y& Elsevier]

Mn-doped films were grown in an ammonia-source HVPE system. Mn3GaN0.5 and GaN were detected in film samples without other phase when the HCl–Mn/NH3 ratio range from 1/200 to 1/100. (GaxMn1-x)N phase also formed in films. Two broad bands centered at 305 and 674 cm-1and new peaks at wave numbers of 592 cm-1arised in Raman spectra of Mn-doped films. It was also found that A1(LO) modes of all Mn-doped samples were strongly asymmetric and showed a considerable redshift. Mn-doped films showed an obvious hysteresis loops at room temperature. Mn-doped films showed metallic characteristic and this mixed structure may be greatly beneficial to spin injection magnetotransport devices. [Copyright &y& Elsevier]

GaN1−xPx ternary alloys with high P compositions were deposited on sapphire substrates by means of metal-organic chemical vapor deposition. Depth profiles of the elements indicate that the maximum P/N composition ratio is about 17% and a uniform distribution of the P atoms in the alloys is achieved. 2θ/ω XRD spectra demonstrate that the (0 0 0 2) peak of the GaN1−xPx alloys shifts to smaller angle with increasing P composition. From the photoluminescence (PL) spectra, the red shifts to the bandedge emission of GaN are determined to be 73, 78, 100 and 87 meV for the GaN1−xPx alloys with the P/N composition ratios of 3%, 11%, 15% and 17%, respectively. No PL peak related to GaP is observed, indicating that the phase separation between GaN and GaP is well suppressed in our GaN1−xPx samples. [Copyright &y& Elsevier]