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Lateral Overgrowth (lateral + overgrowth)
Kinds of Lateral Overgrowth Selected AbstractsEpitaxial lateral overgrowth of GaN on 4 inch Si(111) by MOVPEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Kai Cheng Abstract Epitaxial Lateral Overgrowth (ELOG) of GaN on 4 inch silicon(111) substrates by MOVPE was investigated in this study. ELOG was performed on a GaN template with a couple of AlGaN intermediate layers (IL) on an AlN nucleation layer. The AlGaN ILs supply compressive stress to the top GaN template and thereafter to the ELOG layer. Consequently, layer cracking is minimized. Two masks were used in this work: a 2 inch wagon wheel mask and a 4 inch mask with parallel stripes of various filling factors and periods. The filling factor is varied from 0.33 to 0.7. The periodic spacing is in the range of 6 ,m to 10 ,m. Temperature, V/III ratio, pressure and stripe orientation were optimized to achieve fastest lateral growth rate. The highest lateral to vertical ratio can be more than 4. A fully coalesced layer within the critical thickness for a crack-free layer was achieved on 4 inch silicon substrates. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spatially resolved X-ray diffraction as a tool for strain analysis in laterally modulated epitaxial structuresCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2009A. Wierzbicka Abstract Spatially resolved X-ray diffraction (SRXRD) is applied for micro-imaging of strain in laterally modulated epitaxial structures. In GaAs layers grown by liquid phase epitaxial lateral overgrowth (ELO) on SiO2 -masked GaAs substrates a downward tilt of ELO wings caused by their interaction with the mask is observed. The distribution of the tilt magnitude across the wings width is determined with ,m-scale spatial resolution. This allows measuring of the shape of the lattice planes in individual ELO stripes. If a large area of the sample is studied the X-ray imaging provides precise information on the tilt of an individual wing and its distribution. In heteroepitaxial GaSb/GaAs ELO layers local mosaicity in the wing area is found. By the SRXRD the size of microblocks and their relative misorientation were analyzed. Finally, the SRXRD technique was applied to study distribution of localized strain in AlGaN epilayers grown by MOVPE on bulk GaN substrates with AlN mask. X-ray mapping proves that by mask patterning strain in AlGaN layer can be easily engineered, which opens a way to produce thicker, crack-free AlGaN layers with a higher Al content needed in GaN-based laser diodes. All these examples show that high spatial and angular resolutions offered by SRXRD makes the technique a powerful tool to study local lattice distortions in semiconductor microstructures. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Large area lateral overgrowth of mismatched InGaP on GaAs(111)B substratesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2005S. Uematsu Abstract Application of InGaAs/InGaP double-heterostructure (DH) lasers increases the band offset between the cladding layer and the active layer more than the use of conventional 1.3 µm InGaAsP/InP lasers. As a first step in realizing 1.3 µm InGaP/InGaAs/InGaP DH lasers, we proposed InGaP lattice-mismatched epitaxial lateral overgrowth (ELO) technique and successfully carried out the InGaP growth on both GaAs (100), (111)B and InP (100) substrates by liquid phase epitaxy. In this work, we grew the InGaP crystal on GaAs (111)B substrate by adjusting Ga and P composition in In solution, to obtain In0.79Ga0.21P (, = 820 nm) virtual substrate for 1.3 µm InGaAs/InGaP DH lasers. To grow the InGaP all over the lateral surface of the substrate, the growth time was extended to 6 hours. The amount of InGaP lateral growth up to 2 hours was gradually increased, but the lateral growth was saturated. The InGaP lateral width was about 250 µm at the growth time of 6 hours. We report the result that optical microscope observation, CL and X-ray rocking curve measurements and reciprocal lattice space mapping were carried out to evaluate the crystal quality of the grown InGaP layers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth and Transfer of Monolithic Horizontal ZnO Nanowire Superstructures onto Flexible SubstratesADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Sheng Xu A method of fabricating horizontally aligned ZnO nanowire (NW) arrays with full control over the width and length is demonstrated. A cross-sectional view of the NWs by transmission electron microscopy shows a "mushroom-like" structure. Novel monolithic multisegment superstructures are fabricated by making use of the lateral overgrowth. Ultralong horizontal ZnO NWs of an aspect ratio on the order of ten thousand are also demonstrated. These horizontal NWs are lifted off and transferred onto a flexible polymer substrate, which may have many great applications in horizontal ZnO NW-based nanosensor arrays, light-emitting diodes, optical gratings, integrated circuit interconnects, and high-output-power alternating-current nanogenerators. [source] High efficiency AlGaInN-based light emitting diode in the 360,380 nm wavelength rangePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003Hisao Sato Abstract High performance LEDs emitting in the wavelength range 360,380 nm, are fabricated on sapphire substrates by one-time metalorganic chemical vapor deposition (MOCVD) without using epitaxial lateral overgrowth (ELO) or similar techniques. By improving layer structures and growth conditions, the output power of the LEDs was much improved. The light output power of the LEDs at an injection current of 20 mA is 3.2 mW, 2.5 mW and 1 mW at wavelengths of 378 nm, 373 nm and 363 nm, which correspond to an external quantum efficiency of 4.8%, 3.8% and 1.4%, respectively. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Epitaxial growth of aligned GaN nanowires and nanobridgesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007Kyungkon Kim Abstract Homo-epitaxialy grown aligned GaN nanowires were prepared on crystalline GaN mesas. The GaN nanowires showed preferential growth along the ,100, direction (m -axis direction). By using selectively positioned and crystallographically well defined GaN epitaxial lateral overgrowth (ELO) mesas as substrate, we obtained horizontally aligned GaN nanowires, in comb-like arrays and hexagonal network interconnecting the ELO mesas. Preliminary testing of the nanomechanical behavior of horizontal nanowires is reported. Combination of ELO with nanowire synthesis is expected to provide a new paradigm for nano-electronic and electromechanical devices. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural evaluation of GaN/sapphire grown by epitaxial lateral overgrowth by X-ray microdiffractionPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006M. Drakopoulos The cover picture from the article [1] depicts the geometry of X-ray diffraction on a GaN/sapphire structure made by a two-step epitaxial lateral overgrowth (2S-ELO) process. Below, the X-ray rocking curve as a function of the vertical beam position in 2S-ELO GaN/sapphire is shown. A low intensity line diverging from the main peak position (arrow) may be interpreted as the disappearance of a winged crystal region due to dislocation curvature. This paper is a presentation from the 6th International Conference on Nitride Semiconductors held in Bremen, Germany, in 2005. Further articles from ICNS-6 are also being published in phys. stat. sol. (a) 203, No. 7 (2006) and phys. stat. sol. (c) 3, No. 6 (2006). [source] Improvement of crystal quality of GaN grown on AlN template by MOCVD using HT-AlN interlayerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Tao Yuebin Abstract Two GaN samples, with and without high temperature (HT)-AlN interlayer (labelled as sample A and B, respectively) grown by MOCVD on AlN template, were investigated by double-crystal X-ray diffraction (DC-XRD), photoluminescence (PL), and atomic force microscope (AFM) measurements. It was found that the crystal quality of GaN could be greatly improved by the HT-AlN interlayer. The full width at half maximum (FWHM) of (102) reflection in XRD rocking curve was narrower for sample A than that for sample B. However, the FWHMs of (002) reflections were almost the same for the two samples. In addition, the tilt degree which reflected screw dislocation density was almost the same, while the twist degree which reflected edge dislocation density changed from 0.214° to 0.152° when the HT-AlN interlayer was used. Both the intensities of (102) reflection in XRD and band edge emission in PL for sample A were stronger too. In the AFM images, the atomic growth steps of sample A were clearer than those of sample B. According to the results of the in situ optical reflectivity spectra and the atomic force microscope (AFM) images, the above results were attributed to the three-dimensional (3D) growth mode of the HT-AlN interlayer. The HT-AlN interlayer may work as a kind of "micro-area" seed for epitaxial lateral overgrowth (ELOG) resulting in bending some dislocations. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Improvement in crystalline quality of thick GaInN on m-plane 6H-SiC substrates using sidewall epitaxial lateral overgrowthPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Ryota Senda Abstract We report the fabrication of an epitaxial lateral overgrown (ELO) GaInN layer on a high crystalline-quality-grooved GaN template, which is improved by a sidewall ELO (SELO) technology. The photoluminescence peak intensity of ELO-grown GaInN layer on the SELO GaN underlying layer is twice as high as that of ELO-grown GaInN layer on the m-plane GaN template. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Sidewall epitaxial lateral overgrowth of nonpolar a-plane GaN by metalorganic vapor phase epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Daisuke Iida Abstract A major obstacle to achieving high-performance devices using nonpolar a-plane and m-plane GaN is the existence of high-density threading dislocations and stacking faults. Low-defect-density nonpolar plane GaN films were previously grown by sidewall epitaxial overgrowth using metalorganic vapor phase epitaxy [1, 2]. In this study, we control the growth-rate ratio of Ga-polar GaN to N-polar GaN by adjusting the V/III ratio. It is possible to grow GaN only from the N-face sidewall of grooves by maintaining a high V/III ratio, which reduces the number of coalescence regions on grooves and decreases the threading-dislocation density and stacking-fault density. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Epitaxial lateral overgrowth of GaN on 4 inch Si(111) by MOVPEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Kai Cheng Abstract Epitaxial Lateral Overgrowth (ELOG) of GaN on 4 inch silicon(111) substrates by MOVPE was investigated in this study. ELOG was performed on a GaN template with a couple of AlGaN intermediate layers (IL) on an AlN nucleation layer. The AlGaN ILs supply compressive stress to the top GaN template and thereafter to the ELOG layer. Consequently, layer cracking is minimized. Two masks were used in this work: a 2 inch wagon wheel mask and a 4 inch mask with parallel stripes of various filling factors and periods. The filling factor is varied from 0.33 to 0.7. The periodic spacing is in the range of 6 ,m to 10 ,m. Temperature, V/III ratio, pressure and stripe orientation were optimized to achieve fastest lateral growth rate. The highest lateral to vertical ratio can be more than 4. A fully coalesced layer within the critical thickness for a crack-free layer was achieved on 4 inch silicon substrates. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optimization of underlying layer and the device structure for group-III-nitride-based UV emitters on sapphirePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008K. Iida Abstract Epitaxial lateral overgrowth (ELO) was applied for the growth of AlGaN on a sapphire substrate by metalorganic vapor phase epitaxy. Among several processes, the ELO of AlGaN on grooved AlGaN showed the best surface morphology and the lowest dark-spot density of 1×108 cm,2 as measured using cathodoluminescence. The light output power of a UV LED fabricated on ELO-Al0.25Ga0.75N on grooved Al0.25Ga0.75N was the strongest among several UV LEDs fabricated by different processes. The effect of the Al composition in the electron-blocking (EB) layer on the performance of UV LEDs was investigated. The UV LED with a low-Al-content EB layer showed high output power under a low-injection condition, while the output power of a UV LED with a high-Al-content EB layer did not saturate even under a high-injection condition. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The effect of Ge doping for lattice-mismatched InGaP/InP (100) with epitaxial lateral overgrowthPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2006Kenichi Higuchi Abstract We have proposed the use of 1.3 ,m InGaAs/InGaP laser on an InP (100) substrate to reduce the leakage current. Because of the lattice-mismatch between InP and InGaP, epitaxial lateral overgrowth (ELO) technique is used. Ge doping is an effective way of increasing the amount of lateral growth in InP/InP lattice-matched ELO. In the InGaP/InP lattice-mismatched ELO, the crystal defects of the Ge-doped InGaP layer decrease compared to undoped sample. The Ge doping is effective for growing InGaP/InP with high crystalline quality by ELO. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterization of MOCVD grown GaN on porous SiC templatesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005F. Yun Abstract We have grown GaN layers by MOCVD on a set of nanoporous SiC templates with different porosity and morphology, produced by etching the anodized porous SiC starting material in a H2 environment at temperatures ,1500 °C, in an effort to attain improved films. The hydrogen etching serves to remove surface damage caused during mechanical polishing prior to anodization, remove the skin layer associated with anodization, tune the pore size, and consolidate pore geometry. Growth conditions favoring lateral overgrowth of GaN were employed on this set of samples to obtian GaN to a thickness of 2 µm. Atomically smooth surfaces were obtained for the epitaxial GaN layers. The GaN quality is highly dependent on the specifics of the porous templates used. An intensity increase of up to a factor of 30 was observed in the GaN excitonic peak compared to GaN grown on standard SiC substrate. The I-V data indicated significant reduction in the leakage current (in reverse bias) compared to GaN grown on standard SiC. The dependence of optical properties, crystalline quality, and surface morphology on the particulars of porous SiC templates is discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thick crack-free AlGaN films deposited by facet-controlled epitaxial lateral overgrowthPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003R. Liu Abstract Thick crack-free AlGaN films have been grown on inclined-facet GaN templates. Light emitting diodes with , = 323 nm has been achieved on these epilayers. The GaN template was grown at a low temperature in order to obtain triangle-facet growth fronts. Subsequent growth of AlGaN on this template involving a lateral overgrowth process exhibits interesting properties. The microstructure and optical characterizations were done using transmission electron microscopy and cathodoluminescence. At the AlGaN/GaN interface, a high density of dislocations was created due to lattice mismatch strain. Another unexpected set of triangular boundaries was observed inside the AlGaN layer, which grew without any change of the growth parameters. These boundaries were found to arise from domains grown in different directions. Mono-chromatic cathodoluminescence images indicate that Al content is different between the vertically-grown and the laterally-grown domains, suggesting that lattice mismatch strain exists between them. Dislocations were created at these mismatched boundaries to relax the strain. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural and Optical Properties of Lateral Overgrown GaN Grown by Double Pendeo-Epitaxy TechniquePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003H.S. Cheong Abstract Structural and optical properties of high quality GaN films over the entire surfaces of sapphire substrates employing SiO2 mask-removed double Pendeo-epitaxy technique by metalorganic chemical vapor deposition (MOCVD) were investigated by scanning electron microscopy (SEM), tranmission electron microscopy (TEM), high-resolution X-ray diffraction (HRXRD) and cathodoluminescence (CL). By optimizing the ratio of the lateral to vertical growth rate for the lateral overgrowth of the first and the second window regions of double Pendeo-epitaxial GaN layers, the crystallographic tilt in wing regions was reduced and the propagation of threading dislocations up to the surface of the GaN layers was supressed in their entire region. The luminescence properties of the GaN lyers observed by CL measurement were also improved in their entire region compared to conventional Pendeo-epitaxial growth. [source] | ||||||||||