The epitaxial aluminum nitride (AlN) crystals were grown on c-plane sapphire using high-temperature metal nitride vapor phase epitaxy at the source materials’ different molar flow ratios (V/III ratios). The effects of various V/III ratios on the surface morphology, crystalline quality, material straining, and optical properties of heteroepitaxial AlN thin films were studied using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and photoluminescence (PL). With the increase in the V/III ratio from 1473 to 7367, the substrate surface underwent changes that vary from whiskers to three-dimensional island structures, two-dimensional layered stack structures, and stacked sheet structures. Additionally, due to the presence of nanoscale pits on the substrate surface, almost all samples were tensile stressers. The PL spectra demonstrated the defect luminescence of the epitaxial films, indicating that nitrogen vacancies and oxygen impurities were the samples’ main defects.

I–III–VI chalcopyrite copper indium selenium is one of therepresentatives of the light absorbing layer material, and is often used for a thin-film solar cell. With the development of nano-technology, CuInSe2 quantum dots (CISe QDs) which have intermediate belt and excitation effect characteristics are applied to the solar cells as an alternative of Cd- or S-based QDs. Most conventional methods for the synthesis of CISe QDs using solution involve the dangerous and environmentally unfriendly Oleylamine or phosphine coordination compounds. In this work, CISe QDs were synthesized by a green, safe and low-temperature method in triethylene glycol. Through controlling the growth temperature and time, the diameter can be adjusted from 3[Formula: see text]nm to 10[Formula: see text]nm. The samples exhibit quantum confinement effect, and have a controllable optical band gap. QDs were deposited on the surface of ZnO nanorods to obtain a photoanode, which were fabricated into quantum dot-sensitized solar cells. The device exhibits size-dependent performance. And the open circuit voltage shows a fluctuation up to 0.26[Formula: see text]V. When the size is 4[Formula: see text]nm, the short circuit current density is the largest (15[Formula: see text]mA/cm2).

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In this paper, AlN thin films are fabricated by green and efficient metal nitride vapor phase epitaxy (MNVPE). First, AlN films are grown on c‐plane sapphire substrates at different molar flow ratios (V/III ratios) of the source material, and the effects of V/III on the crystal quality and surface morphology of the films are investigated. The growth conditions are kept constant (growth temperature of 1550 °C, growth pressure of 10 kPa, V/III ratio of 4420), and the AlN thin films are prepared by heterogeneous epitaxial growth on c‐plane sapphire, silicon (111), and GaN substrates. The crystal quality, residual stress, and luminescence properties of epitaxial AlN thin films on the three substrates are investigated using X‐ray diffraction, scanning electron microscopy, Raman spectroscopy, photoluminescence, and UV spectrophotometer. Among them, the FWHM value of the sample AlN/GaN (002) plane can reach 338 arcsec. The residual stress in samples AlN/Sapphire, AlN/GaN and AlN/Si are 1027, −81, and −541 MPa, respectively, and the sample AlN/GaN has fewer point defects. At the same time, a 50‐nanometer‐thick void layer appears in the AlN thin film samples prepared on GaN substrates, which provides a new technical idea for realizing large‐scale and high‐quality self‐supporting AlN thin films.

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