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Metalorganic Chemical Vapor Deposition (metalorganic + chemical_vapor_deposition)
Selected AbstractsInAs quantum dot formed on GaNAs buffer layer by Metalorganic Chemical Vapor DepositionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2006R. Suzuki Abstract We investigated MOCVD grown InAs QDs on a GaNAs buffer layer. Distribution uniformity and shape of QDs on buffer layers were characterized for different nitrogen (N) compositions from 0% to 2%. It was found that the distribution of QDs on a GaNAs buffer layer became more uniform than that on a GaAs and the coalescence of QDs was suppressed. Increase of the aspect ratio (diameter/height) was also observed by increase of N composition. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Heteroleptic Guanidinate- and Amidinate-Based Complexes of Hafnium as New Precursors for MOCVD of HfO2EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2010Ke Xu Abstract The synthesis and characterization of four new heteroleptic complexes [Hf{,2 -(iPrN)2CNMe2}2Cl2] (1), [Hf{,2 -(iPrN)2CNMe2}2Me2] (2), [Hf{,2 -(iPrN)2CMe}2Cl2] (3), and [Hf{,2 -(iPrN)2CMe}2Me2] (4) are reported. All the complexes were characterized by spectroscopic methods, while compounds 1,3 were further examined by single-crystal X-ray diffraction, revealing that the complexes are monomers with the hafnium center in a distorted octahedral geometry. The thermal properties of the chlorine-free complexes (2, 4) were examined to determine their suitability for metalorganic chemical vapor deposition (MOCVD) applications, and compound 2 showed good volatility and thermal stability. On the basis of these results, compound 2 was selected for MOCVD of HfO2 with oxygen as oxidant. Depositions were carried out on Si(100) substrates in the temperature range 300,700 °C. The as-deposited HfO2 films crystallized in the monoclinic phase at temperatures above 500 °C, and the composition analysis determined by Rutherford back-scattering (RBS) and X-ray photoelectron spectroscopy (XPS) revealed that the films were stoichiometric and free of carbon. Thus, alkylguanidinatohafnium complex 2 is a promising precursor for growing HfO2 films in a wide temperature range with the desired stoichiometry, because of its adequate volatility, sufficient temperature window between vaporization and decomposition, as well as its ability to decompose cleanly in the presence of oxygen. [source] High Purity GaAs Nanowires Free of Planar Defects: Growth and Characterization,ADVANCED FUNCTIONAL MATERIALS, Issue 23 2008Hannah J. Joyce Abstract We investigate how to tailor the structural, crystallographic and optical properties of GaAs nanowires. Nanowires were grown by Au nanoparticle-catalyzed metalorganic chemical vapor deposition. A high arsine flow rate, that is, a high ratio of group V to group III precursors, imparts significant advantages. It dramatically reduces planar crystallographic defects and reduces intrinsic carbon dopant incorporation. Increasing V/III ratio further, however, instigates nanowire kinking and increases nanowire tapering. By choosing an intermediate V/III ratio we achieve uniform, vertically aligned GaAs nanowires, free of planar crystallographic defects, with excellent optical properties and high purity. These findings will greatly assist the development of future GaAs nanowire-based electronic and optoelectronic devices, and are expected to be more broadly relevant to the rational synthesis of other III,V nanowires. [source] Self-organized InAs quantum dots grown in a V-groove InGaAs quantum wirePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2007Chang-Sik Son Abstract Self-organized InAs quantum dots (QDs), by the Stranski,Krastanow mode, have been grown by using low-pressure metalorganic chemical vapor deposition on V-groove GaAs substrates. By adjusting the flow rate of AsH3 during the growth of InAs QDs, a one dimensional InAs QD array was successfully formed along the [01] direction only at the bottom of V-grooves. No QDs were observed on the sidewalls and the surface of the mesa top. The InAs QDs took on an oval shape. They were spatially well-isolated along the [01] direction with a line density of 3 × 103 cm,1. These low-density InAs QDs are expected to be used in areas of quantum information and quantum computing. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical, structural, and magnetic properties of p-type GaN implanted with Fe+ (5 and 10 at%)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2007Yoon Shon Abstract p-type GaN epilayers were prepared by metalorganic chemical vapor deposition and subsequently implanted with Fe+. The results of energy dispersive X-ray peak displayed the Fe-injected concentration of 5 and 10 at%, respectively. The results of photoluminescence measurement show that optical transitions related to Fe appear at 2.5 and 3.1 eV. It was confirmed that the photoluminescence peak at 2.5 eV is a donor-Fe acceptor transition and the photoluminescence peak at 3.1 eV is a conduction band-Fe acceptor transition. Apparent ferromagnetic hysteresis loops measured at 10 and 300 K with the Fe concentration of 10 at% were observed, and the temperature-dependent magnetization displayed a ferromagnetic behavior persisting up to 300 K. The systematic enhancement of ferromagnetic hysteresis loops for GaN implanted with high doses of Fe (5 , 10 at%) takes place with an increase in the annealing temperature from 700 to 850 °C. The trends of magnetic properties coincide with the results of the increased full width at half maximum of triple axis diffraction for GaN (0002) including the appearance of GaFeN, the enhanced Fe-related photoluminescence transitions, and the increased sizes of symmetric spin ferromagnetic domains GaFeN in atomic force microscopy and magnetic force microscopy systematically. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [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] Preparation of extended microtunnels in GaN by wet chemical etchingPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007Hsin-Hsiung Huang Abstract Extended microtunnels with triangular cross sections are demonstrated in GaN layers on sapphire substrates. The depths of the tunnels can easily reach several hundred micrometers by using wet chemical etching. To obtain this result, patterned growth of specially designed GaN layers is carried out on sapphire substrates with metalorganic chemical vapor deposition and subsequently hydride vapor-phase epitaxy techniques. The prepared samples are then chemically etched in molten potassium hydroxide, and microtunnels with triangularly etched cross sections are formed. The planes of the triangular bevels belong to the {112} family. The etch rate of the tunnel can be as high as 10 ,m/min under proper etching conditions. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Stranski,Krastanow growth of stacked GaN quantum dots with intense photoluminescencePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003K. Hoshino Abstract Multiple-layer stacked GaN quantum dots (QDs) with intense photoluminescence (PL) have been grown by the Stranski,Krastanow growth mode in metalorganic chemical vapor deposition. Scanning transmission electron microscopy (STEM) analysis shows that the vertical aligned QDs are formed, which results from a strain field induced by buried islands. We have also investigated PL spectra at room temperature. The PL intensity increases with increasing number of the stacked layer. This indicates that the carriers can be injected into each layer of GaN quantum dots. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical properties of InGaN/GaN MQW microdisk arrays on GaN/Si(111) templatePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Kang Jea Lee Abstract We report the fabrication of InGaN/GaN multi quantum well (MQW) microdisk arrays on Si(111) substrates. InGaN/GaN MQWs were grown on highly tensile-strained GaN films on Si(111) substrate by metalorganic chemical vapor deposition. Microdisk resonators were fabricated using a combination of optical lithography, a dry GaN-etching process, and Si undercut etching by acid chemical solution. The evidence of whispering-gallery modes in optically pumped microdisk cavities have been observed by photoluminescence. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fully unstrained GaN on sacrificial AlN layers by nano-heteroepitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007K. Tonisch Abstract Usually, the fabrication of microelectromechanical systems (MEMS) requires unstrained or tensile strained active layers on a selectively removable sacrificial layer, since compressive strain causes instabilities due to buckling effects. For group III-nitride based MEMS, AlN is a promising material for sacrificial layers since it can be epitaxially overgrown and etched selectively to GaN. However, due to the larger lattice constants GaN is growing compressively strained on AlN. Nanoheteroepitaxy opens a way to yield fully unstrained, high quality epitaxial GaN layers on nanocrystalline AlN thin film by means of a 3D strain relaxation mechanism. For this purpose sputtered nanocrystalline AlN films were overgrown with single crystalline GaN and AlGaN/GaN layers by metalorganic chemical vapor deposition. The high quality of the layers is proven by an atomically flat surface and a 2D electron gas at the interface of the AlGaN/GaN heterostructure (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Buffer breakdown voltage of AlGaN/GaN HFET on a 4 inch Si(111) substrate grown by MOCVDPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007Masayuki Iwami Abstract The buffer breakdown voltage and the electron mobility in a two dimensional gas (2DEG) of AlGaN/GaN HFETs on 4 inch Si(111) substrates grown by metalorganic chemical vapor deposition was investigated. The relationship between the electrical properties of HFETs and the crystalline quality of the GaN layer are studied by X-ray diffraction and photoluminescence measurements. The buffer breakdown voltage decreases with an increase in the FWHM of the X-ray (0002) diffraction peak. The electron mobility in a 2DEG decreases with an increase in FWHM of the X-ray (102) diffraction peak. These results indicate that a screw component of the threading dislocations in the GaN layer is a primary source for buffer leakage, and that edge dislocations in the GaN layer have a scattering effect on the 2DEG transport. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] n-Al0.75Ga0.25N epilayers for 250 nm emission ultraviolet light emitting diodesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005W. H. Sun Abstract We have developed a unique approach combining migration-enhanced metalorganic chemical vapor deposition (MEMOCVD) high temperature AlN buffer layers and AlGaN/AlN superlattices (SLs) to yield high quality ( HQ) AlGaN layers for 250 nm LEDs. Symmetric/asymmetric X-ray diffraction (XRD) and room temperature photoluminescence measurements were used to study the high-structural and optical quality. The (002) and (114) rocking curve full width at half,maximum (FWHM) of 1.4 µm n-Al0.75Ga0.25N grown over AlGaN/AlN buffer were 143 and 565 arcsec, respectively. Crack-free Al0.75Ga0.25N layers with electron concentration as high as 1 × 1018 cm,3 and Hall mobility about 50 cm2/V.s were successfully grown and used for sub-milliwatt power (0.12 mW at a pulse pump current of 300 mA) 250 nm deep ultraviolet light emitting diodes (UVLEDs). In addition, for comparison, we prepared n-AlGaN only using high temperature AlN without SLs inserted. The experiments show that the AlGaN/AlN SLs inserted play a crucial role in improving structural and optical quality of high Al-composition AlGaN epilayers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Direct observation of hillocks on pendeo-epitaxial GaN films and stabilization of GaN seed layers for hillock-free surfacePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003H. S. Cheong Abstract Hillocks formed on pendeo-epitaxial GaN (PE-GaN) films grown by metalorganic chemical vapor deposition were observed by scanning electron microscopy, atomic force microscopy and high-resolution transmission electron microscopy. In order to suppress hillock formation on PE-GaN films, a two-step growth technique was employed. In the first-step growth, whose growth temperature and V/III ratio were relatively low, it was necessary to suppress hillock formation on the surface, and reduce the crystallographic tilt in the wing regions of PE-GaN films. In the second-step growth, whose growth temperature and V/III ratio were relatively high, complete coalescence without tilt in the wing regions was achieved by a high lateral growth rate. [source] Structural and electrical characterization of a -plane GaN grown on a -plane SiCPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003M. D. Craven Abstract Planar nonpolar () a -plane GaN thin films were grown on () a -plane 6H-SiC substrates via metalorganic chemical vapor deposition by depositing a high temperature AlN buffer layer prior to the epitaxial GaN growth. The orientation of the GaN film and AlN buffer layer directly match that of the SiC substrate, as determined by on- and off-axis X-ray diffraction measurements. The morphological evolution of GaN grown on the AlN buffer layers was investigated using atomic force microscopy. Microstructural characterization of the coalesced a -plane GaN films provided by plan-view transmission electron microscopy revealed threading dislocation and stacking fault densities of ,3 × 1010 cm,2 and ,7 × 105 cm,1, respectively. Structural comparisons to a -plane GaN films grown on r -plane sapphire substrates are presented. Si-doped films were grown with a variety of Si/Ga ratios and electrically characterized using Hall effect measurements. A maximum Hall mobility of 109 cm2/Vs was attained at a carrier concentration of 1.8 × 1019 cm,3. [source] Effects of Mg fluctuation on the electrical and optical properties in p-GaN/undoped GaN layers dependent on the growth temperaturePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003C. S. Kim Abstract The effects of heavly Mg doping dependent on the growth temperature of p-GaN layers grown on undoped GaN layers by metalorganic chemical vapor deposition (MOCVD) on electrical and optical properties were studied by capacitance,voltage (C,V) and temperature-dependent photoluminescence (TDPL), respectively. At high growth temperature of p-GaN above 1110 °C, optical microscopy images as well as atomic force microscopy (AFM) images show polygonal hillocks on heavily Mg-doped GaN surface. It was also found that fluctuation of Mg concentration ([Mg]) measured by secondary ion mass spectroscopy (SIMS) was increased with increasing growth temperature. These phenomena were appeared to decrease NA,ND and change PL emission from 3.1,3.2 eV of conduction band-to-shallow Mg acceptor (e, A) transition to 2.8,2.9 eV of Mg-related deep donor-to-acceptor pair (DAP) transition. [source] The growth of In-rich InGaN/GaN single quantum wells by metalorganic chemical vapor depositionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Hyun Jin Kim Abstract In-rich InGaN/GaN single quantum wells were grown by metalorganic chemical vapor deposition for the first time to the best of our knowledge. The structures consist of a 2-,m thick GaN buffer layer, a 2-nm thick In-rich InGaN single quantum well, and a 20 nm thick GaN capping layer. Single quantum well structures were examined by transmission electron microscopy. Photoluminescence emissions from the single quantum well samples were observed at wavelengths ranged from 400 nm to 500 nm depending upon the growth conditions of the InN layer. From a simple energy level calculation, we found the possibility of extremely large emission peak shift with well thickness. [source] Optical properties of InAs/InP quantum dot stack grown by metalorganic chemical vapor depositionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2003Heedon Hwang Abstract The 5-layer InAs quantum dot (QD) stack was grown on an (001) InP substrate by low pressure-metalorganic chemical vapor deposition. 40 nm InP spacer layers were inserted between the InAs QDs. The integrated intensity of the photoluminescence peak at 300 K was over 12% of that at 10 K. Far-infrared absorption peaks were observed at 819 cm,1 (101.64 meV) and 518 cm,1 (64.08 meV) from this structure at room temperature by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Raman analysis showed that the peak at 819 cm,1 was attributed to a plasmon related peak in the n-type InP substrate. The absorption peak at 518 cm,1 was regarded as a peak related with intersubband transition in the InAs QDs, suggesting that room temperature operating quantum dot devices may be fabricated. [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] Metallic Li in carbonaceous nanotubes grown by metalorganic chemical vapor deposition from a metalorganic precursorAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2008Mahua Das Abstract Metallic Li in carbonaceous nanostructures was obtained in high concentration (as much as 33.4%) through metalorganic chemical vapor deposition involving certain lithium,aminoalkyl moieties, which are formed in situ, by decomposition of a precursor containing both cobalt and lithium. The bimetallic complex containing both lithium and cobalt was characterized by IR spectroscopy, mass spectroscopy, nuclear magnetic resonance spectroscopy, elemental analysis and thermogravimetric analysis. X-ray photoelectron spectroscopy measurements performed on the as-grown films demonstrate that lithium can be stable in metallic form in such a film. Results of X-ray photoelectron spectroscopic analysis of the as-grown films are presented as direct evidence of the formation and stabilization of metallic lithium in carbon nanotubes. Carbon nanotubes, encapsulating metallic lithium, can potentially act as a miniaturized nanobattery. Such a battery would be potentially useful in the next generation of communication and remote sensing devices, where a pulse of current is required for their operation. In addition, with metallic lithium, having an effective nuclear magnetic moment, such materials can be envisioned to show potential applications in devices based on nuclear magnetic resonances. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||