Selective incorporation of Si along step edges during delta-doping on MOVPE-grown GaAs (001) vicinal surfaces

We investigated the delta-doping (δ-doping) of Si using SiH₄ on MOVPE-grown GaAs (001) vicinal surfaces to explore the possibility of selective incorporation of Si along atomic steps, and to demonstrate doping quantum wires by the combination of multiatomic steps and wire-like doping. It was found that the doping density on vicinal surfaces was enhanced as the misorientation angle was increased, which suggested the enhanced decomposition of SiH₄ and the selective incorporation of Si at step edges. It was also found that this selective incorporation could be enhanced by annealing the surface prior to the δ-doping, which resulted from the reduced incorporation of Si at the terrace regions. Anisotropic electron transport properties which are expected from the wire-like incorporation along step edges are also discussed.     

Selective growth experiments on gallium arsenide (1 0 0) surfaces patterned using UV-nanoimprint lithography

We describe a nanoimprint lithography (NIL) process and subsequent solid-source molecular beam epitaxy (SSMBE) growth of III–V semiconductors on patterned substrates. In particular, growth of GaAs, GaInAs, and GaInP, and effects of growth temperature were studied using AFM, SEM, and XRD. It turns out that selective growth of GaAs on patterned substrates is relatively straightforward, but GaInAs and GaInP are more challenging. For the first time, GaInP has been selectively grown on UV-NIL-patterned substrates using SSMBE.     

Relative reactivities of halogen-substituted substrates (R-Br, R-Cl) toward the halophilic attack by a carbanion

Relative reactivities of bromine-substituted substrates (R-Br) or chlorine-substituted substrates (R-CI) toward bromophilic or chlorophilic attack by a carbanion have been evaluated by the intermolecular competition kinetics. Relative reactivity orders are CF₃CFBr₂> CF₃CBr₃≥CBr₄ > CHBr₃ > CF₃CFBrCF₂Br > CF₂Br₂ > BrCF₂CF₂Br > BrCH₂CO₂Et ≥ BrCF₂CFHBr > CH₂Br₂ > BrCH₂CH₂Br, and CI₃CNO₂ > CI₃CCN > CI₃CCOPh > cyclo-C₅CI₆ > CI₃CCOCI > CCI₃CF₂CI > CCI₃CF₃ ≥ CCI₄ > CCI₃CCI₃ ≥ CCI₃(CF₂)₂CI > CI₃CCOCCI₃ > CCI₃(CF₂)₆CI > CI₃CCO₂Et > CI₃CF > CI₃CPh > CI₃CCH₂O₂CCH₃.     

Fabrication and Characterization of Large Free-Standing Polarizer Grids for Millimeter Waves

Construction of large aperture free-standing metal wire grids is demonstrated for the lower end of the millimeter wave spectral region. For the constructed two grids the co-polarized and cross-polarized components of transmitted power were measured at 45° oblique incidence. The measurements were performed as a function of wire orientation angle and in more detail at selected angles. The results are in good agreement with the theoretical results presented in the literature. In order to save time and costs the construction apparatus was simplified from those reported previously by other authors. It was shown that for this frequency range the grid characteristics are not degraded when such an apparatus is applied. One of the constructed grids will be used in a calibration system of the Helsinki University of Technology (HUT) polarimetric radiometer.     

Flat GaN epitaxial layers grown on Si(111) by metalorganic vapor phase epitaxy using step-graded AlGaN intermediate layers

In this work, we report on the growth by metalorganic vapor phase epitaxy (MOVPE) of GaN layers on AlN/Si(111) templates with step-graded AlGaN intermediate layers. First, we will discuss the optimization of the AlN/Si(111) templates and then we will discuss the incorporation of step-graded AlGaN intermediate layers. It is found that the growth stress in GaN on high-temperature (HT) AlN/Si(111) templates is compressive, although, due to relaxation, the stress we have measured is much lower than the theoretical value. In order to prevent the stress relaxation, step-graded AlGaN layers are introduced and a crack-free GaN epitaxial layer of thickness >1 μm is demonstrated. Under optimized growth conditions, the total layer stack, exceeding 2 μm in total, is kept under compressive stress, and the radius of the convex wafer bowing is as large as 119 m. The crystalline quality of the GaN layers is examined by high-resolution x-ray diffraction (HR-XRD), and the full-width-at-half maximums (FWHMs) of the x-ray rocking curve (0002) ω-scan and (−1015) ω-scan are 790 arc sec and 730 arc sec, respectively. It is found by cross-sectional transmission electron microscopy (TEM) that the step-graded AlGaN layers terminate or bend the dislocations at the interfaces.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

无掩模硅图形衬底上3C-SiC的异质外延生长

采用低压化学气相沉积方法在无掩模的硅图形衬底上异质外延生长3C-SiC.硅图形衬底采用光刻和ICP刻蚀得到.图形由平行长条状沟槽和台面组成,其中沟槽宽度为1～10μm不同间隔,沟槽之间距离为1～10μm不同间隔.对于在不同的沟槽和台面尺寸区域3C-SiC的生长进行了详细研究.采用扫描电镜分别观察了不同区域的生长形貌,分析了图形衬底结构上SiC的生长行为.其中合并生长形成的空气隙结构可以释放由Si和SiC晶格失配引起的应力,从而可以用来解决SiC生长中的晶片翘曲问题,进行厚膜生长.XRD结果表明此无掩模硅图形衬底上得到3C-SiC(111)取向生长.     

Comparison of MBE Growth of InSb on Si (001) and GaAs (001)

We describe the epitaxial growth of InSb films on both Si (001) and GaAs (100) substrates using molecular-beam epitaxy and discuss the structural and electrical properties of the resulting films. The complete 2 μm InSb films on GaAs (001) were grown at temperatures between 340°C and 420°C and with an Sb/In flux ratio of approximately 5 and a growth rate of 0.2 nm/s. The films were characterized in terms of background electron concentration, mobility, and x-ray rocking curve width. Our best results were for a growth temperature of 350°C, resulting in room-temperature mobility of 41,000 cm²/V s.  For the growth of InSb on Si, vicinal Si(001) substrates offcut by 4° toward (110) were used. We investigated growth temperatures between 340°C and 430°C for growth on Si(001). In contrast to growth on GaAs, the best results were achieved at the high end of the range of T _S =  C, resulting in a mobility of 26,100 cm²/V s for a 2 μm film. We also studied the growth and properties of InSb:Mn films on GaAs with Mn content below 1%. Our results showed the presence of ferromagnetic ordering in the samples, opening a new direction in the diluted magnetic semiconductors.     

用于HDI和IC基板的低-CTE碳纤维复合材料

文章概述了HDI板和IC基（载）板面临着低-CTE基材的挑战。而低-CTE碳纤维复合材料是优选的最佳化的CCL材料。     

Temperature dependence of growth orientation and surface morphology of Li‐doped ZnO thin films on SiO2/Si substrates

ZnO thin films doped with Li (ZnO:Li) were deposited onto SiO₂/Si (100) substrates by direct‐current sputtering technique in the temperature range from room temperature to 500 °C. The crystalline structure, surface morphology and composition, and optical reflectivity of the deposited films were studied by X‐ray diffraction (XRD), Scanning Electron Microscopy (SEM), X‐ray Photoelectron Spectroscopy (XPS) and optical reflection measurements. Rough surface p‐type ZnO thin film deposition was confirmed. The results indicated that the ZnO:Li films growed at low temperatures show c‐axis orientation, while a‐axis growth direction is preferable at high temperatures. Moreover, the optical reflectivity from the surface of the films matched very well with the obtained results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)