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The ZnO films were grown by low pressure metal-organic chemical vapor deposition (LP-MOCVD) using dimethylzinc (DMZn) and oxygen. The as-grown film has strong (0002) oriented characteristic, containing the chain-like network grains in small sizes, A well-resolved shoulder emission at 3.03 eV in the photoluminescence (PL) spectra has been ascribed to the interstitial zinc in the crystal, implying a serious oxygen deficiency state of the MOCVD growth, in good agreement with the analysis of XPS results. Post-annealing of the films leads to the remarkable improvement of the structure, morphology, components and optical properties. Large hexagonal columnar grains were then observed by atomic force microscope (AFM). The luminescence efficiency was enhanced greatly due to the reduction of the nonradiative defects. Meanwhile, chemisorbed oxygen gives rise to surface acceptor states, resulting in the different radiative recombination. Photoluminescence excitation measurement shows good agreement with the above conclusions. [ABSTRACT FROM AUTHOR]

The GaN-rich side of GaNP ternary alloys has been successfully synthesized by light-radiation heating and low-pressure metal-organic chemical vapor deposition. X-ray diffraction (XRD) rocking curves show that the (0002) peak of GaNP shifts to a smaller angle with increasing P content. From the GaNP photoluminescence (PL) spectra, the red shifts from the band-edge emission of GaN are determined to he 73, 78 and 100 meV, respectively, in the GaNP alloys with the P contents of 1.5%, 5.5% and 7.5%. No PL peak or XRD peak related to GaP is observed, indicating that phase separation induced by the short-range distribution of GaP-rich regions in the GaNP layer has been effectively suppressed. The phase-separation suppression in the GaNP layer is associated with the high growth rate and the quick cooling rate under the given growth conditions, which can efficiently restrain the accumulation of P atoms in the GaNP layer. [ABSTRACT FROM AUTHOR]

3C-SiC was heteroepitaxially grown on Si(1 1 1) substrates by the low pressure chemical vapor deposition (LPCVD) with a gas mixture of silane, ethane and hydrogen. Under the very low pressure of 30 Pa, we got good single-crystalline SiC films at a low temperature of 900 °C, much lower than the typical deposition temperature above 1200 °C found elsewhere. Their characteristics and crystallinity were examined by X-ray diffraction, infrared absorption, and auger electron spectrum (AES). The SiC peak was found at a 2θ value of 35.8°. The full width at half maximum (FWHM) is only 0.28°, indicating that the SiC film is single crystalline. In the FTIR absorption a peak at 800 cm−1 is observed. In the AES depth profile the film is composed of Si and C with a composition very close to that of stoichiometric SiC. The surface morphology of the film was examined by AFM. These images show the good crystalline of SiC at the surface, and the surface image of a film grown at the initial stage was also observed in order to study the growth mechanism at low temperature and low pressure. [Copyright &y& Elsevier]

The strained Si layer has been grown on the relaxed 3C–SiC virtual substrate by a hot-wall low-pressure chemical vapor deposition (LPCVD) system. The relaxed SiC virtual substrate was grown on Si(1 1 1) substrate by LPCVD and the crystal quality of the layer is characterized by X-ray diffraction and Fourier transform infrared absorption spectroscopy. It is apparent to find three regions in the Auger electron spectroscopy depth profile graph of the sample, which refer to the cap Si layer, the relaxed 3C–SiC virtual substrate and the Si(1 1 1) substrate, respectively. The bonding states of the relaxed 3C–SiC virtual substrate in the sample are analyzed by X-ray photoelectron spectroscopy. The Raman spectra of the sample indicate the cap Si layer is strained. A high hole Hall mobility value of 889 cm2/V s (300 K) is obtained in the strained Si layer, which is due to the in-plane compressive biaxial strain in this layer. [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: High reflectivity (>93.5%) distributed Bragg reflectors (DBRs) have been successfully produced using the AlGaN/AlN multilayer stacks materials system by metal-organic chemical vapor deposition (MOCVD). The peak reflectance of the DBRs was located at 320nm. The nominal Al composition is 30%, and the layer thicknesses of the different periods stack were designed for a target wavelength of 330nm. We present reflectivity, SEM, AFM and XRD data of Al x Ga1− x N/AlN Bragg reflectors grown on (0001)-oriented sapphire. The surface of the AlN/AlGaN DBRs was found to grow in quasi-two-dimensional (2D) mode, which was indicated by the atomic force microscopy (AFM). The DBR has very smooth surface and the interface was distinct. [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]

Abstract: High-quality single-crystal Ga-doped ZnO films have been epitaxially deposited on (0002) sapphire substrate by low-pressure metal organic chemical vapor deposition (MOCVD) technique. The dependence of structural, electrical and optical properties of films on Ga doping concentration was investigated. As grown at the Ga/Zn gas ratio of 3.2at%, the film shows a narrow linewidth of 0.26° for ZnO (0002) peak, high carrier concentration of 2.47×1019 cm−3, and high optical transparency over 90%. The carrier concentration increased sharply and became saturated at higher doping level due to the onset of carrier compensation. The Burstein–Moss blueshift of the absorption edge energy increased as expected with the carrier concentration up to 2.47×1019 cm−3. In addition, doping-induced photoluminescence (PL) emission linewidth broadening and bandgap renormalization (BGR) effects have also been observed. The intensity of PL emission decreased with increasing Ga dopant concentration, which was believed to be a direct consequence of the doping-enhanced nonradiative recombination rates. [Copyright &y& Elsevier]

Abstract: Indium nitride (InN) films have been deposited on sapphire substrates at 350–500 °C using low-pressure metalorganic chemical vapor deposition (LP-MOCVD). Increasing the growth temperature changes the structure of InN from cubic to hexagonal. At 500 °C, no InN can be grown on sapphire due to its decomposition. The X-ray diffraction (XRD) spectra of InN films show that the diffractions from In(101) reach a maximum at 425 °C and begin to decrease at the growth temperature higher than 425 °C. According to the scanning electron microscope (SEM) images of InN films, the In aggregation on the surface is observed at the growth temperature of 425 °C, which corresponds to the most intensive diffraction of In(101) in XRD spectra. In addition, the density of InN nucleation sites is reduced by increasing the growth temperature. As well as the increase of In desorption with the growth temperature, the decrease of InN nucleation sites are responsible for the most significant In aggregation at 425 °C. [Copyright &y& Elsevier]

The Mn-implanted GaN with ferromagnetism at room temperature has been prepared successfully. The optical and structural properties of Mn-implanted GaN films have been investigated. The films studied were grown by metal organic chemical vapor deposition, with Mn implanted in 150 keV, which can offer many distinguished advantages compared with other doping methods. A new energy band with a minimum at 2.9 eV in the reflectance spectra has been observed. The yellow band emission was greatly decreased according to the result of photoluminescence. The results of vibrating sample magnetometer experiment proved the ferromagnetic properties of Mn-doped GaN at room temperature. [Copyright &y& Elsevier]