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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]

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: 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: Structural and optical properties of a-SiN x films deposited by electron cyclotron resonance chemical vapor deposition (ECRCVD) have been investigated. The Fourier transform infrared (FTIR) spectroscopy shows the structural evolution of the SiN x films, which are defined as Si-rich SiN x and N-rich SiN x films, also confirmed by Raman spectroscopy. The origin of the light emission for SiN x films may be attributed to two mechanisms, i.e., quantum confinement effect (QCE) and transition of defect energy levels. The correlation between light emission and structures of SiN x films is discussed. [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]

Photoluminescence (PL), X-ray diffraction (XRD) and Raman spectra have been measured to characterize the effects of phosphorus on the optical and structural properties of GaN1−xPx alloys with x&les;15%, grown by means of light-radiation heating, low-pressure metal-organic chemical vapor deposition. The PL spectra of GaN1−xPx show the largest red shift of 100 meV from the band-edge emission of GaN. XRD rocking curves show that the (0 0 0 2) peak of GaN1−xPx shifts to smaller angles with increasing P content. The Raman spectra of GaN1−xPx, recorded in backscattering geometry, exhibit four new vibrational modes at 256, 314, 377 and 428 cm−1 compared with an undoped GaN sample. The modes at 377 and 428 cm−1 are attributed to gap modes related to the Ga–P bond vibrations, whereas the other two modes at 256 and 314 cm−1 are assigned to phosphorus clusters and disorder-activated scattering, respectively. The frequency of the A1 (LO) mode is found to decrease with increasing x at a much high rate of approximately 268 cm−1/x for x<0.03. This red shift is attributed to the effects of alloying and strain. Furthermore, we have not observed characterizations related to GaP resulted from the phase separation from PL, XRD and Raman spectra of all investigated 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]