The crystallinity of laser-recrystallized Si films on insulators ͑SOI films͒ was characterized by micro-Raman imaging. A small-angle bevel made by angle lapping of the SOI film was used to probe the structure at different depths. The Raman signals that varied with the position along the tilt show that interference of both the incident and scattered light induced in the angle-lapped specimens results in periodic enhancements in the intensity as a function of film thickness. An analysis of the fringe patterns in the Raman images provides us with depth profiles of strain and structural disorders with a high depth resolution on a scale of a few tens of nanometers. When moving away from the interface between the silicon film and the insulator, the peak frequency of the polycrystalline silicon band shifts to the lower frequency side and the band width becomes smaller. The depth profile of the Raman feature shows that the defect density is high in the region near the interface of Si and SiO 2 , and that the stress increases toward the top surface of the silicon film. Moreover, a partial relaxation of the stress occurs near the interface region due to the generation of a high density of defects.

We report a high-efficiency source of cross-polarized photon pairs via type-II quasi-phase matched spontaneous parametric down-conversion using periodically poled lithium niobate (PPLN). The photon pairs are generated from the PPLN in a fifth-order quasi-phase matching condition around 800 nm, which matches the wavelength band of efficient Si avalanche photodiodes. We obtained the photon-pair production rate of 6.8×105 s-1 mW-1.

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Effect of (GaN/AlN) alternating‐source‐feeding (ASF) buffer layer was investigated in the growth of GaN on Al2O3 and Si substrates by radio‐frequency plasma‐assisted molecular beam epitaxy (RF‐MBE). The formation process of ASF buffer layer was different between the cases on Al2O3 and Si substrates. Nevertheless, GaN films with two‐dimensional surface were obtained on both ASF buffer layers on Al2O3 and Si substrates. The residual strain of GaN films was changed by changing the growth condition of the ASF buffer layers. Without any selection of substrates, it is expected to achieve the precisely controlled strain state of GaN films by adjusting the structure of the ASF buffer layer. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

GaN-based UV Schottky-type (ST) LEDs were fabricated using GaN layers grown by molecular beam epitaxy (MBE). Red, green, and blue (RGB) pixels were fabricated using the UV-LEDs and RGB phosphors. Surface modification led to the reduction in reverse-bias leakage current and improved forward-bias characteristics. It was found that the ideality factor, n, was improved with increasing breakdown voltage in the reverse-bias range. We believe that the improvement is due to the reduced number of threading-dislocation (TD)-related leakage paths. The effect of the point defects around the TDs on light emission was reduced by the surface modification because the number of current paths around the TDs was reduced.