Search

InGaN epitaxial layers were grown on c-plane sapphire substrates using the metalorganic vapour phase epitaxy (MOVPE) system at 760 °C. By varying the total flow rate of group-III sources (TMI+TEG) with a fixed molar ratio of group-III sources [TMI/(TMI+TEG)], the influence of V/III ratio were investigated from 4500 to 20000. The grown N-polar InGaN layers were investigated by atomic force microscopy and it is found that the surface roughness decreases with increasing the V/III ratios. High resolution X-ray diffraction analyses show that the phase separation decreases with increasing the V/III ratios. Photoluminescence measurements reveal that the peak position of the band-edge emission shifted toward the shorter wavelength with increasing the V/III ratios. Reciprocal space mapping (RSM) analyses were carried out on InGaN films. At low V/III ratio, the phase separation can be detected in InGaN films.

As a novel substrate with a lattice-mismatch of only 0.8% along the a-axis to InN thin films, we propose LaBGeO5 (LBGO) with a trigonal symmetry for the first time. A single crystal growth of LBGO by Czochralski (Cz)-pulling was investigated, and c-axis-oriented LBGO single crystals with high crystallinity were successfully grown with a pulling rate of 0.5 mm/h in O2-atomosphere. c-axis oriented InN film was subsequently grown on the obtained LBGO {001} substrate by metalorganic vapor epitaxy (MOVPE), and it was verified that InN film on LBGO was less-strained as compared with that on {001} sapphire substrate. It is stressed to say that LBGO can be expected as a lattice-matching substrate for the epitaxial growth of InN.

We report the characteristics of AlN:Er films that were co-deposited by using AlN, Er, and SiO 2 targets. The PL emission spectra show strong green emissions of Er 3+ ions in AlN:Er films annealed at an optimal temperature of 750 °C, which is attributed to the intra-4 f Er 3+ transitions of 2 H 11/2 → 4 I 15/2 and 4 F 7/2 → 4 I 15/2 . This optimal temperature can activate Er species as an efficient visible luminescence center. High-resolution transmission electron microscopy (HREM) observations showed that the AlN:Er film annealed at 750 °C exhibits the microstructure of AlN nanocrystallites embedded in the amorphous matrix. The occurrence of strong Er 3+ emissions in the amorphous–nanocrystalline AlN:Er films by thermal annealing might contribute to an increased number of excitation Er 3+ centers and the presence of oxygen related to Er 3+ excitation and recombination processes. A distinct visible bluish green emission is also confirmed from the EL device with an amorphous–nanocrystalline AlN:Er active layer.

β-Iron disilicide (FeSi 2 ) single crystals were grown by the chemical vapor transport (CVT) with iodine (I 2 ) as a transport agent. The optical and electrical properties of the crystals were then studied. Raman spectrum shows a set of strong A g -mode peaks and photoluminescence (PL) spectra show a very broad emission band. In order to study the effect of annealing on the electrical properties, β-FeSi 2 single crystals were annealed in the range of 1073–1213 K for 48 h. The electrical properties of as-grown and annealed crystals were then evaluated by measuring their Hall effects in the temperature range of 10–300 K. The results show that both of the as-grown and annealed single crystals are of the n-type conductivity. The dependences of the temperature indicate that carrier concentration decreases and Hall mobility increases with the increase of measuring temperature. When the annealing temperature reaches above 1223 K, these changes tend to saturation. Furthermore, the donor ionization energies were estimated and the scattering mechanisms of carrier were discussed.

This study showed that substrate rotation plays an important role in the growth of high-quality β -FeSi 2 epitaxial film on hydrogen terminated Si (1 1 1) substrate using molecular beam epitaxy (MBE). The present work elucidated the substrate rotation effects on morphology, thickness, and purity. Results verified that substrate rotation is essential to grow thicker epilayers with better morphology and compositional uniformity. In addition, purity analyses indicated that substrate rotation increases the concentration of non-metallic impurities (H, C, and O), but does not further introduce metallic impurities into β -FeSi 2 films.

In order to grow β-FeSi2 single crystals by the chemical vapor transport (CVT) method, the growth conditions, including density of iodine transport agent and growth duration, were examined. An iodine density of 8.9 mg cm–3 was thought to be optimum in the present experiment. It was found that the growth duration should be over 4 weeks for growing β-FeSi2 single crystals. X-ray structural analysis revealed that the growth direction of the β-FeSi2 crystals was The growth rate along the directions with lower Miller indexes was slower than that along the directions with higher Miller indexes. The measured lattice constants were a = 0.986 nm, b = 0.780 nm, and c = 0.781 nm. These values are consistent with the previously reported values. Hall measurements showed that the electron mobility was over 350 cm2 V–1 s–1 at 10 K. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The effect of the growth temperature on InN films grown at 500-725 °C by the pressurized–reactor metal organic vapor phase epitaxy (PR-MOVPE), which is designed to apply high nitrogen pressure to the reactor, has been studied. The growth temperature is found to greatly influence the surface morphology. The columnar islands appear at the growth temperature lower than and equal to 575 °C while the coalescence of islands occurs and forms continuous films at the growth temperature higher than 575 °C. Step-flow-like morphology is actually observed in the growth temperature range as high as 600-650 °C.However, at this high growth temperature range, the diffraction peak of metallic indium appears in XRD spectra. Therefore, it is in a dilemma to enhance the surface migration and prevent the precipitation of metallic indium. Our experimental results indicate that the growth temperature of InN can be increased using the pressurized growth conditions and the epitaxial temperature around 575 °C is best to obtain a good crystalline quality InN films without the precipitation of metallic indium at present growth pressure. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The signs of the off-angle toward +c-direction of the miscut m-GaN substrates indicated in Figs. 1 and 2 and in the text should be reversed. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)