Showing papers on "Nitride published in 2007"

Design and characterization of GaN∕InGaN solar cells

Abstract: We experimentally demonstrate the III-V nitrides as a high-performance photovoltaic material with open-circuit voltages up to 2.4V and internal quantum efficiencies as high as 60%. GaN and high-band gap InGaN solar cells are designed by modifying PC1D software, grown by standard commercial metal-organic chemical vapor deposition, fabricated into devices of variable sizes and contact configurations, and characterized for material quality and performance. The material is primarily characterized by x-ray diffraction and photoluminescence to understand the implications of crystalline imperfections on photovoltaic performance. Two major challenges facing the III-V nitride photovoltaic technology are phase separation within the material and high-contact resistances.

2-phosphor-converted white light-emitting diodes using oxynitride/nitride phosphors

Abstract: Green α-sialon:Yb2+ and red Sr2Si5N8:Eu2+ oxynitride/nitride phosphors have been demonstrated as potential downconversion luminescent materials for white light-emitting diodes (LEDs). In this letter, the authors attempt to fabricate white LEDs by combining α-sialon:Yb2+ and Sr2Si5N8:Eu2+ with a blue LED die and report their optical properties. These two phosphors lend themselves for use in 2-phosphor-converted white LEDs with promising properties: a wide range of tunable correlated color temperature (2700–6700K), acceptable color rendering index (82–83), and luminous efficacy (17–23lm∕W). These LEDs are acceptable for general lighting.

Preparation of CaAlSiN3:Eu2+ Phosphors by the Self-Propagating High-Temperature Synthesis and Their Luminescent Properties

Abstract: Divalent europium-doped nitride phosphors, Ca1-xEuxAlSiN3 (x = 0−0.2), were successfully prepared by the self-propagating high-temperature synthesis (SHS) by using Ca1-xEuxAlSi alloy powder as a precursor. The Rietveld refinement analysis was carried out on the CaAlSiN3 host lattice to elucidate the luminescence properties of dopant Eu2+ on the tetrahedrally coordinated site. For the Eu2+ doped samples, strong absorption peaking at about 460 nm was observed on the excitation spectra, which matched perfectly with the current blue light of InGaN/GaN light-emitting diodes (LEDs). The optimized sample, Ca0.98Eu0.02AlSiN3, gave the red emission peaking at 649 nm of which the intensity was competitive with the sample prepared from the metal nitride raw materials (Ca3N2, AlN, Si3N4, and EuN). The CIE chromaticity index (0.647, 0.347) with high color saturation indicated that it was a promising candidate as a red-emitting phosphor for the InGaN/GaN-based down-conversion white LEDs for general illumination or disp...

Large Magnetic Anisotropy of a Single Atomic Spin Embedded in a Surface Molecular Network

Abstract: Magnetic anisotropy allows magnets to maintain their direction of magnetization over time. Using a scanning tunneling microscope to observe spin excitations, we determined the orientation and strength of the anisotropies of individual iron and manganese atoms on a thin layer of copper nitride. The relative intensities of the inelastic tunneling processes are consistent with dipolar interactions, as seen for inelastic neutron scattering. First-principles calculations indicate that the magnetic atoms become incorporated into a polar covalent surface molecular network in the copper nitride. These structures, which provide atom-by-atom accessibility via local probes, have the potential for engineering anisotropies large enough to produce stable magnetization at low temperatures for a single atomic spin.

Light emitting diodes (leds) with improved light extraction by roughening

Abstract: Systems and methods are disclosed for fabricating a semiconductor light emitting diode (LED) device by forming an n-gallium nitride (n-GaN) layer on the LED device; and roughening the surface of the n-GaN layer to extract light from an interior of the LED device.

Dilute nitride GaInNAs and GaInNAsSb solar cells by molecular beam epitaxy

Abstract: Dilute nitride films with a roughly 1 eV band gap can be lattice-matched to gallium arsenide and germanium, and therefore could become a critical component in next-generation multijunction solar cells. To date most dilute nitride solar cells have been plagued with poor efficiency, due in large part to short diffusion lengths. This study focuses on two techniques aimed at improving the quality of dilute nitride films grown by molecular beam epitaxy: the utilization of biased deflection plates installed in front of the nitrogen plasma source, and the introduction of antimony during growth. Results from GaInNAs cells grown with and without deflection plates, and GaInNAsSb solar cells are reported. The use of biased deflection plates during GaInNAs growth improved every aspect of solar cell performance. For the GaInNAs devices grown with deflection plates, the dark current density, open-circuit voltage, and fill factor were the best of the devices studied. The GaInNAsSb cells had the highest quantum efficienc...

Method for forming strained silicon nitride films and a device containing such films

Abstract: A method for forming a strained SiN film and a semiconductor device containing the strained SiN film. The method includes exposing the substrate to a gas including a silicon precursor, exposing the substrate to a gas containing a nitrogen precursor activated by a plasma source at a first level of plasma power and configured to react with the silicon precursor with a first reactivity characteristic, and exposing the substrate to a gas containing the nitrogen precursor activated by the plasma source at a second level of plasma power different from the first level and configured to react with the silicon precursor with a second reactivity characteristic such that a property of the silicon nitride film formed on the substrate changes to provide the strained silicon nitride film.

Electronic structure, chemical bonding and elastic properties of the first thorium‐containing nitride perovskite TaThN3

Abstract: The full-potential linearized augmented plane wave method with the generalized gradient approximation for the exchange and correlation potential (LAPW-GGA) is used to understand the electronic and elastic properties of the first thorium-containing nitride perovskite TaThN3. Total and partial density of states, charge distributions as well as the elastic constants, bulk modulus, compressibility, shear modulus, Young modulus and Poisson ratio are obtained for the first time and analyzed in comparison with cubic ThN. The chemical bonding in TaThN3 is a combination of ionic Th–N and of mixed covalent–ionic Ta–N bonds. The cubic TaThN3 is semiconducting with the direct gap at about 0.65 eV. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Water permeation through a subnanometer boron nitride nanotube.

Abstract: Boron nitride nanotubes (BNNTs) have been shown to possess many excellent physical properties, including thermal and mechanical properties. In this work, we report on superior water permeation properties of BNNTs. Specifically, using molecular dynamics simulations, we found that water molecules permeate through the (5,5) boron nitride nanotube, while a (5,5) carbon nanotube (CNT) of approximately the same diameter does not conduct water. The relatively strong interactions between the nitride atoms of the BNNT and water molecules play a key role in the continuous wetting behavior of the BNNT. The properties of water, such as the axial diffusion coefficient and the hydrogen bonding, inside the (5,5) BNNT were found to be comparable to those inside the (6,6) CNT, even though the diameter of the (5,5) BNNT is about 1.3 A smaller than that of the (6,6) CNT.

Improved External Extraction Light Emitting Diode based upon Crystallographic Faceted Surfaces

Abstract: A light emitting diode is disclosed that includes a support structure and a Group III nitride light emitting active structure mesa on the support structure. The mesa has its sidewalls along an indexed crystal plane of the Group III nitride. A method of forming the diode is also disclosed that includes the steps of removing a substrate from a Group III nitride light emitting structure that includes a sub-mount structure on the Group III nitride light emitting structure opposite the substrate, and thereafter etching the surface of the Group III nitride from which the substrate has been removed with an anisotropic etch to develop crystal facets on the surface in which the facets are along an index plane of the Group III nitride. The method can also include etching the light emitting structure with an anisotropic etch to form a mesa with edges along an index plane of the Group III nitride.

Breakthroughs in Improving Crystal Quality of GaN and Invention of the p−n Junction Blue-Light-Emitting Diode Breakthroughs in Improving Crystal Quality of GaN and Invention of the p−n Junction Blue-Light-Emitting Diode

Abstract: Marked improvements in the crystal- line quality of GaN enabled the production of GaN-based p−n junction blue-light-emitting and violet-laser diodes. These robust, ener- getically efficient devices have opened up a new frontier in optoelectronics. A new arena of wide-bandgap semiconductors has been developed due to marked improvements in the crystalline quality of nitrides. In this article, we review breakthroughs in the crystal growth and conductivity control of nitride semicon- ductors during the development of p−n junc- tion blue-light-emitting devices. Recent prog- ress mainly based on the present authors' work and future prospects of nitride semicon- ductors are also discussed. Group III nitride semiconductors are recog- nized as one of the most promising materials for fabricating optical devices in the visible short-wavelength and UV region. To develop such novel devices and clarify the intrinsic materials properties of nitrides, it is essential to grow high-quality single crystals and control their electrical conductivity. However, high- quality epitaxial GaN was impossible to grow and its conductivity was uncontrollable. These problems have prevented the development of GaN-based p−n junction blue-light-emitting devices for many years. 1) In 1986, we achieved a marked improve- ment in the crystal quality of GaN which enabled us to realize p-type conduction in nitrides and to control the conductivity of n-type nitrides in 1989. In the same year, these achievements led to the invention of the world's first GaN p−n junction blue/UV-light- emitting diode (LED). In 1990, stimulated emis- sion in the UV region at room-temperature (RT), which is indispensable for laser action, was also achieved. These breakthroughs inspired nitride researchers around the world to exert great effort, which eventually led to the commercialization of high-performance blue LEDs and long-lifetime violet-laser diodes (LDs), and to the development of nitride-based devices such as UV detectors and high-speed field-effect transistors.

Modulating etch selectivity and etch rate of silicon nitride thin films

Abstract: Etching of nitride and oxide layers with reactant gases is modulated by etching in different process regimes. High etch selectivity to silicon nitride is achieved in an adsorption regime where the partial pressure of the etchant is lower than its vapor pressure. Low etch selectivity to silicon nitride is achieved in a condensation regime where the partial pressure of the etchant is higher than its vapor pressure. By controlling partial pressure of the etchant, very high etch selectivity to silicon nitride may be achieved.

Enhancement mode gallium nitride power devices

Abstract: Enhancement mode III-nitride devices are described The 2DEG is depleted in the gate region so that the device is unable to conduct current when no bias is applied at the gate Both gallium face and nitride face devices formed as enhancement mode devices

Ultraviolet semiconductor laser diodes on bulk AlN

Abstract: Current-injection ultraviolet lasers are demonstrated on low-dislocation-density bulk AlN substrates. The AlGaInN heterostructures were grown by metalorganic chemical vapor deposition. Requisite smooth surface morphologies were obtained by growing on near-c-plane AlN substrates, with a nominal off-axis orientation of less than 0.5°. Lasing was obtained from gain-guided laser diodes with uncoated facets and cavity lengths ranging from 200 to 1500 μm. Threshold current densities as low as 13 kA/cm2 were achieved for laser emission wavelengths as short as 368 nm, under pulsed operation. The maximum light output power was near 300 mW with a differential quantum efficiency of 6.7%. This (first) demonstration of nitride laser diodes on bulk AlN substrates suggests the feasibility of using such substrates to realize nitride laser diodes emitting from the near to deep ultraviolet spectral regions.

Properties of titanium nitride films prepared by direct current magnetron sputtering

Abstract: Titanium nitride (TiN) thin films of different thickness were deposited by direct current (dc) magnetron sputtering under conditions of various N2 concentrations (05–34%) The electrical, optical, structural, compositional and morphological properties of the films were studied and the results were discussed with respect to N2 concentration and thickness of the films At low N2 concentration of 05% (of the total sputtering pressure 11 Pa), golden coloured stoichiometric TiN films were obtained and with increase in the N2 concentration non-stoichiometric TiNx phases resulted However, irrespective of the N2 concentration, the TiN stoichiometry in the films increased with increase in the film thickness In the surface of the films the presence of nitride (TiN), oxynitride (TiOxNy) and oxide (TiO2) phases were observed and the quantity of these phases varied with the N2 concentration and thickness The films of lower thickness were found to be amorphous and the crystallinity was observed in the films with increase in the thickness The crystalline films showed reflections corresponding to the (1 1 1), (2 0 0) and (2 2 0) orientation of the cubic TiN and also features associated with TiNx phases The transmission spectra of the films revealed the typical characteristics of the TiN films ie a narrow transmission band, however, the width varied with thickness, in the wavelength range of 300–600 nm and exhibited low transmission in the infrared region The TiN films deposited at low N2 concentration of 05% showed smooth and uniform morphology with densely packed crystallites With increase in N2 concentration various characteristics such as needle type crystallization, bubble precipitates and after bubble burst morphologies were observed in the films However, at higher N2 concentration conditions, uniformity developed in the films with increase in thickness

Endohedral clusterfullerenes—playing with cluster and cage sizes

Abstract: The family of endohedral fullerenes was significantly enlarged within the past six years by the clusterfullerenes containing structures like the M2C2 carbides and the M3N nitrides. While the carbide clusters are generated under the standard arc burning conditions according to the stabilisation energy the nitride clusterfullerene type is formed by varying the composition of the cooling gas atmosphere in the arc burning process. The special situation in nitride clusterfullerene synthesis is described in detail and the optimum conditions for the production of nitride clusterfullerenes as the main product in fullerene synthesis are discussed. A review of new nitride clusterfullerenes reported recently is given summarizing the structures, properties and the stability of metal nitride clusterfullerenes. It is shown that all cages with even carbon atoms of C68 and beyond are available as endohedral nitride clusterstructures. Furthermore the nitride clusterfullerenes are that class of endohedral fullerenes forming the largest number of non-IPR structures. Finally the prospects of this evolving field are briefly discussed taking the superior stability of these endohedral clusterfullerenes into account.

Method and system for dry etching a metal nitride

Abstract: PROBLEM TO BE SOLVED: To provide a method and a system for dry-etching a metal nitride such as a titanium nitride or the like. SOLUTION: The method for dry-etching includes a step of introducing a treatment component including a halogen containing gas such as Cl 2 , HBr, BCl 2 or the like, and a fluorocarbon gas having a chemical formula C x H y F z , wherein x and z are 1 or more and y is 0 or more. COPYRIGHT: (C)2009,JPO&INPIT

Method for forming nitride crystals

Abstract: A method for growing a nitride crystal and a crystalline composition selected from one of A1N, InGaN, A1GaInN, InGaN, and A1GaNInN is provided. The composition comprises a true single crystal, grown from a single nucleus, at least 1 mm in diameter, free of lateral strain and tilt boundaries, with a dislocation density less than about 104 cm-2.

Silicon Quantum Dots in a Dielectric Matrix for All-Silicon Tandem Solar Cells

Abstract: We report work progress on the growth of Si quantum dots in different matrices for future photovoltaic applications. The work reported here seeks to engineer a wide-bandgap silicon-based thin-film material by using quantum confinement in silicon quantum dots and to utilize this in complete thin-film silicon-based tandem cell, without the constraints of lattice matching, but which nonetheless gives an enhanced efficiency through the increased spectral collection efficiency. Coherent-sized quantum dots, dispersed in a matrix of silicon carbide, nitride, or oxide, were fabricated by precipitation of Si-rich material deposited by reactive sputtering or PECVD. Bandgap opening of Si QDs in nitride is more blue-shifted than that of Si QD in oxide, while clear evidence of quantum confinement in Si quantum dots in carbide was hard to obtain, probably due to many surface and defect states. The PL decay shows that the lifetimes vary from 10 to 70 microseconds for diameter of 3.4 nm dot with increasing detection wavelength.

NROM fabrication method

Abstract: A method of fabricating an oxide-nitride-oxide (ONO) layer in a memory cell to retain charge well in the nitride layer includes the steps of forming a bottom oxide layer on a substrate, depositing a nitride layer and oxidizing a top oxide layer, thereby causing oxygen to be introduced into the nitride layer. Another method includes the steps of forming a bottom oxide layer on a substrate, depositing a nitride layer and oxidizing a portion of a top oxide layer, thereby causing oxygen to be introduced into the nitride layer and depositing a remaining portion of the top oxide layer, thereby assisting in controlling the amount of oxygen introduced into the nitride layer. A further method includes the steps of forming a bottom oxide layer on a substrate, depositing a nitride layer, depositing a portion of a top oxide layer and oxidizing a remaining portion of the top oxide layer, thereby causing oxygen to be introduced into the nitride layer.

Systems and methods of forming refractory metal nitride layers using organic amines

Abstract: A method of forming (and apparatus for forming) refractory metal nitride layers (including silicon nitride layers), such as a tantalum nitride barrier layer, on a substrate by using an atomic layer deposition process (a vapor deposition process that includes a plurality of deposition cycles) with a refractory metal precursor compound, an organic amine, and an optional silicon precursor compound.

Heterojunction device comprising a semiconductor and a resistivity-switching oxide or nitride

Abstract: In the present invention a metal oxide or nitride compound which is a wide-i band-gap semiconductor abuts a silicon, germanium, or alloy of silicon and/or germanium of the opposite conductivity type to form a p-n heteroj unction. This p-n heteroj unction can be used to advantage in various devices. In preferred embodiments, one terminal of a vertically oriented p-i-n heterojunction diode is a metal oxide or nitride layer (118), while the rest of the diode is formed of a silicon or silicon-germanium resistor; for example a diode may include a heavily doped n-type silicon region (4), an intrinsic silicon region (6), and a nickel oxide layer (118) serving as the p-type terminal. Many of these metal oxides and nitrides exhibit resistivity-switching behavior, and such a heterojunction diode can be used in a nonvolatile memory cell, for example in a monc-lithic three dimensional memory array.