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β-Ga2O3 films were grown on sapphire (0001) substrates with various O/Ga (VI/III) ratios by metal organic chemical vapor deposition. The effects of VI/III ratio on growth rate, structural, morphological, and Raman properties of the films were systematically studied. By varying the VI/III ratio, the crystalline quality obviously changed. By decreasing the VI/III ratio from 66.9 × 103 to 11.2 × 103, the crystalline quality improved gradually, which was attributed to low nuclei density in the initial stage. However, crystalline quality degraded with further decrease of the VI/III ratio, which was attributed to excessive nucleation rate. [ABSTRACT FROM AUTHOR]

β gallium oxide (β-Ga 2 O 3) is a promising material for the detection of solar-blind ultraviolet (SBUV). The quality of β-Ga 2 O 3 crystal has a crucial influence on the performance of the photodetectors (PDs). In this paper, SBUV PDs were fabricated on high quality homoepitaxial β-Ga 2 O 3 films grown by metal organic chemical vapor deposition (MOCVD). Both photoconductor PD and Schottky barrier diode (SBD) PD were prepared. The PDs showed excellent performance. For the photoconductor PD, the responsivity and EQE under the illumination of 254 nm light at 20 V bias were respectively 1.08 A/W and 5.32 × 102%. For the SBD PD, the I 254 /I dark at −20 V was 320, and the corresponding rejection ratio I 254 /I 365 was 42. • Solar-blind ultraviolet photodetectors were fabricated on high quality homoepitaxial β-Ga 2 O 3 films grown by MOCVD. • Both photoconductor photodetector and SBD photodetector were fabricated. • The photodetectors showed excellent detection performance. [ABSTRACT FROM AUTHOR]

We fabricated the light-emitting diodes (LEDs) consisting of n-ZnO/p-NiO/p-Si heterostructure by using metal-organic chemical vapor deposition (MOCVD) combined with radio frequency (RF) magnetron sputtering. The devices exhibited diode-like rectifying current–voltage characteristics and had a turn-on voltage of 6.8 V. Under forward bias, a prominent broad emission peaked around 400–650 nm was observed at room temperature. The asymmetric electroluminescence (EL) spectra were consisted of two apparent bands, which located at 420 and 495 nm corresponding to the violet and green luminescence, respectively. Furthermore, the mechanism of the light emission was tentatively discussed in terms of the band diagrams of the heterojunction. [ABSTRACT FROM AUTHOR]

Abstract: We report the growth of atomically smooth N-polar GaN on c-plane sapphire by metalorganic vapor phase epitaxy. A two-step growth technique was adopted; low-temperature growth of GaN buffer before high-temperature GaN growth. The complete two-dimensional N-polar GaN growth process was recorded by in situ reflectance. The phase composition of the low-temperature GaN was examined by X-ray diffraction pole figure measurements. The thickness of the low-temperature GaN buffer dramatically affected the crystalline and electronic properties of the N-polar GaN. A very small full width at half maximum for the (0002) X-ray rocking curve, 51arcs, was obtained for 700-nm-thick N-polarity GaN by optimizing the buffer thickness. [Copyright &y& Elsevier]

Abstract: Normally, surface of c-axis oriented YBCO films grown by MOCVD are found to be populated by micron-sized outgrowths with elemental compositions such as Ba–Cu–O and Cu–O. For both low and high current applications with the YBCO films, these surface outgrowths should be eliminated. In this study, it is found that by using a simple processing technique of decreasing appropriately the sublimation temperature of the Cu-based precursor, the surface outgrowths can be essentially subdued. At the same time it is qualitatively predictable that J c of these smoother YBCO films will be lowered. However, experimentally, it is found that at appropriate YBCO film growth conditions, the lowered J c value is acceptable for most applications. Actually, a surface outgrowth covered YBCO film made by photo-assisted MOCVD, with film composition Y:Ba:Cu as 1:1.2:1.5, has its J c being 3.4MA/cm2 (0T, 77K). As composition of YBCO film is changed to 1:0.9:1.2 by lowering the sublimation rate of the Cu-based precursor, then there are no more outgrowths on surface, with its J c being 2.6MA/cm2. [Copyright &y& Elsevier]

Abstract: It is well-known that there is a relatively small temperature window for the growth of epitaxial and c-axis oriented YBCO thin films by various methods. In this study, this window was more precisely examined for YBCO film growths by photo-assisted MOCVD. At specified total reactor pressure of 4.6torr, and specified respective partial pressures for the oxidizing agents, O2 and N2O at 1.7torr and 1.1torr, the film growths were tested at several substrate temperature (T s) points from 780°C to 864°C. The film growth time for each test was 3min. As to compositional purity, purity in c-axis orientation, and crystal structural quality of these tested films by using photo-assisted MOCVD technique, it was found that for the growth of purely c-axis oriented YBCO thin films with high crystalline quality, the appropriate growth temperature range (or “T s window”) was from about 800°C to 830°C, at relevant pressures as specified above. T c and J c of a typical YBCO film sample grown within this “T s window”, i.e., 810°C, were found as 90K and 1.32MA/cm2 (77K, 0Oe) respectively by magnetization measurements. It is noticeable that this film, and other purely c-axis oriented YBCO films are all single-crystal like and dense, with no SEM visible grain boundary or void. The causes of precipitates found on top surface of these c-axis oriented YBCO films are also discussed. [Copyright &y& Elsevier]

High-quality ZnO films were grown on epi-GaN predeposited on c-Al2O3 substrates using low-pressure metal-organic chemical vapor deposition (MOCVD). Detailed study of the X-ray diffraction spots and patterns by different diffractometers showed high structural perfection of the zinc oxide layer, which indicated that the growth of ZnO film was strongly c-oriented. The full-width at half-maximum (FWHM) of the ω-rocking curve was 0.39°. Surface morphology of the films studied by AFM showed that the growth of the ZnO film followed the regular hexagonal column structure with about 500 nm grain diameter. Zn and O elements in the deposited ZnO/GaN/Al2O3 films were investigated and compared by X-ray photoelectron spectroscopy (XPS), in which the dissociative O and Zn atom peak was hardly observed. The ratio of O/Zn atoms of the film was about 1 with O-rich. Photoluminescence spectra of the ZnO films grown on epi-GaN showed dominating exciton emission peak, and the deep-level emission which was obvious on ZnO/Al2O3 film had hardly been observed. [Copyright &y& Elsevier]

β gallium oxide (β-Ga 2 O 3) homoepitaxy films were grown on (2 ‾ 01) β-Ga 2 O 3 substrates by metal organic chemical vapor deposition (MOCVD). The effect of growth temperature on the crystalline quality was measured and systematically analyzed. The results showed the growth temperature played an important role in crystalline quality of β-Ga 2 O 3. The optimized single crystalline β-Ga 2 O 3 film was grown at 750 °C, and the full width at half maximum (FWHM) of X-ray diffraction (XRD) rocking curve was 21.6 arcsec, smaller than that of the β-Ga 2 O 3 substrate (26.3 arcsec). The film exhibited a greatly smooth surface and the root-mean-square (RMS) roughness was 0.68 nm. And the arrangement of atoms inside the film was in good accordance with lattice constants of β-Ga 2 O 3. In addition, the effect of the band structure on the luminescent properties of β-Ga 2 O 3 was discussed. • The crystalline quality of the optimized film was superior to that of the substrate. • Atomic arrangement inside the β-Ga 2 O 3 films was displayed. • The effect of band structure on the luminescent properties of β-Ga 2 O 3 was discussed. [ABSTRACT FROM AUTHOR]