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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]

ZnO films were prepared on (0002) sapphire by metal-organic chemical vapor deposition (MOCVD) with fixed Zn and O gas flow rates. The film properties displayed complex dependencies on temperature over the range 330–460 °C. All films were preferentially oriented along the (0002) direction and the integrated intensity of the (0002) peak increased with increasing substrate temperature, indicative of an increasing deposition rate. Furthermore, high substrate temperatures promoted the growth of columnar grains, and improved the crystallinity, as the decreasing FWHM of the (0002) ZnO peak suggests. However, it was not the highest temperature sample, but the sample deposited at 390 °C that had the best UV band emission characteristics, with no defect-related luminescence in the photoluminescence (PL) spectra, as well as the highest transmission and sharpest absorption edge in the transmittance spectra. [ABSTRACT FROM AUTHOR]

Abstract. The oxidation of GaN epilayers in dry oxygen has been investigated. The GaN epilayers, about 1 micro m thick, were grown on (0001) sapphire substrates by rapid thermal process/low pressure metalorganic chemical vapor deposition. Bulk theta - 2 theta X-ray diffraction (XRD) data showed that the slight oxidation of GaN began to occur at 800 Celsius tot 6 h. The oxide was identified as the monoclinic beta-Ga[sub 2]O[sub 3]. The GaN epilayers were completely oxidized at 1050 Celsius for 4 h or at 1100 Celsius for I h. For all samples, the strongest oxide's peak is (11-3), and (30-6) followed. There is a rapid oxidation process in the initial stage of oxidation, and a relatively slow process followed when the temperature was over 1000 Celsius. The oxidation of two stages was limited by the rate of an interracial reaction mechanism and by the diffusion mechanism, respectively. When the temperature reaches 1100 Celsius, the oxidation rate is very fast, which is considered as the results of the GaN decomposition at high temperature under atmosphere. The oxide layers were also observed by a scanning electron microscope, which shows a rough oxide surface and an expansion of the volume of 40%. The photoluminescence (PL) seriously influenced by the oxidation is also discussed. [ABSTRACT FROM AUTHOR]

Abstract. Epitaxial growth of high-quality hexagonal GaN films on sapphire substrates using light-radiation heating metal-organic chemical vapor deposition (LRH-MOCVD) is first reported. The deposition temperature is 950 Celsius, about 100 Celsius lower than that in normal rf-heating MOCVD growth. The FWHM of GaN (0002) peak of the X-ray diffraction rocking curve is 8.7 arc min. Photoluminescence spectrum of GaN film shows that there is a very strong band-edge emission and no "yellow-band" luminescence. Hall measurement indicates that the n-type background carrier concentration of GaN film is 1.7 x 10[sup 18]cm[sup -3] and the Hall mobility of it is 121.5 cm[sup 2]/V s. It is suggested that the radiation of light in GaN growth enhances the dissociation of ammonia and decreases the disadvantages of the parasite reaction between trimethylgallium and ammonia. [ABSTRACT FROM AUTHOR]

Abstract. Thin heteroepitaxial films of Si[sub 1-x-y]Ge[sub x]C[sub y] have been grown on Si(100) substrates by rapid thermal chemical vapor deposition (RTCVD) using C[sub 2]H[sub 4] as C source. The composition and microstructure of Si[sub 1-x-y]Ge[sub x]C[sub y] films were characterized by Auger electron spectroscopy, Raman spectra and Fourier-transform infrared spectroscopy. The results show that lower temperature and higher SiH[sub 4]/C[sub 2]H[sub 4] flow ratio are helpful in forming the substitutional C and improving the crystal quality. A possible mechanism for C incorporation in Si[sub 1-x-y]Ge[sub x]C[sub y] layers grown by RTCVD using C[sub 2]H[sub 4] is proposed. [ABSTRACT FROM AUTHOR]

Abstract. Ge-rich Ge[sub 1-x-y]Si[sub x]C[sub y] alloys have been grown on Si (100) substrates by plasma-enhanced rapid thermal chemical vapor deposition. It is found that there is a strong suppressive effect of C on the Ge composition and the growth rate. A possible mechanism for the suppressive effect is proposed. After calculations of atomic configuration, we obtain the relationship between the degree of suppression and the Ge/C atomic ratio. From the calculation results, a saturation tendency of the suppressive effect is expected with increasing Ge concentration in the growth of Ge[sub l-x-y]Si[sub x]C[sub y] alloys. [ABSTRACT FROM AUTHOR]

Cubic silicon carbide (3C-SiC) has been grown on Si (111) substrate by chemical vapor deposition. The crystal quality of SiC with the SiCN buffer layer is obviously improved comparing with that grown on the SiC buffer layer. The SiCN film, composed of elemental Si and SiC 1-x N x alloy, is formed by the constant-source diffusion of the C and N atoms into the Si substrate. During the 3C-SiC high temperature growth, this in-situ formed SiCN film evolves into a double sub-layered SiCN buffer, including the SiC 1-x N x alloy and the SiCN composite sub-layers. The SiC 1-x N x alloy layer ( x from 0 to 0.09) results from the limited-source diffusion of N from the in-situ formed SiCN film to the subsequently deposited SiC. The SiCN composite layer, composed of elemental Si and SiC 1-x N x alloy ( x from 0.09 to 0.06), is caused by the constant-source diffusion of C from the SiC towards the substrate, as well as the outgoing diffusion of N in the in-situ formed SiCN film. The SiCN buffer layer can effectively accommodate the lattice mismatch between SiC and Si substrate. [ABSTRACT FROM AUTHOR]

The SiCN film, which has the same crystal structure as 3C-SiC verified by X-ray diffraction and Raman scattering, has been formed on Si (111) substrate by constant-source diffusion using a chemical vapor deposition system. Via X-ray photoelectron spectroscopy, the film has been identified as the mixture of elemental Si and SiC 1 − x N x alloy, with the SiC 1 − x N x content decreases from 87.4% to 17.9% and the mole fraction x increases from 0.17 to 0.21, as the depth extends from the near surface to the interface. The measured composition distribution can be well explained by the constant-source diffusion model, confirms that the formation mechanism of the SiCN film is the diffusion of C and N into the Si substrate. This provides a new method for fabricating crystalline SiCN thin films. [ABSTRACT FROM AUTHOR]

Abstract: The fluid dynamics of a vertical metal-organic chemical vapor deposition (MOCVD) reactor for the growth of ZnO film have been studied. The relevant transport equations were solved by numerical integration using a finite volume difference method. Computation results show that the deposition rate strongly depends on the operating parameters of the MOCVD reactor. Simulation results show that the reactor pressure has effect on the deposition rate, which becomes larger with the increment of the reactor pressure in the range of low pressure in our study. The simulated deposition rate is observed to increase firstly and then decrease with the main carrier gas flow rate. The computational study demonstrates that the distance between the O2 inlet and substrate in the vertical MOCVD reactor plays a key role to obtain a balance between the deposition rate and the uniformity of films across the substrate. The optimization of the MOCVD operational parameters has been applied in the MOCVD growth of high-quality ZnO epilayers. [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: 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]

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]

Abstract: By using chemical vapor deposition method, 4H-SiC films have been grown on AlN/Si(100) complex substrates at the temperature below 1100 °C. Substitutional Al and N are found in the SiC film. Photoluminescence (PL) peaks, related to Al acceptor and N shallow donor, respectively, have been observed at the room-temperature. The higher partial pressure ratio of SiH4 and C2H4 (P C2H4 / P SiH4 ≧1.62) results in more Si-vacancy (V Si) in the film. The PL peak related to the V Si acceptor level is also observed. [Copyright &y& Elsevier]