bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sb-terminated InAs(001)-(2×4) and (2×8) studied using scanning tunneling microscopy and ab initio density functional theory
Authors: Barvosa-Carter William , Grosse Frank , Owen James H. G. , Zinck Jennifer J. 
Published: April 2011

AbstractWe have studied the structure of MBE-grown InAs(001)-(2×4) surfaces exposed to low Sb2 fluxes by scanning tunneling microscopy (STM) and ab initio density functional theory (DFT). Experimentally, we observe an Sb-terminated α2(2×4) phase over a wide range of temperatures (400–510 °C) for low Sb2 flux (<0.1 ML/s), whereas temperature and As2 flux must be carefully controlled to achieve the same As-terminated surface structure. At lower temperatures, we observe indications of an Sb-terminated (2×8) symmetry surface phase, and we report briefly on its proposed structure and stability, as well as its possible role in subsequent formation of the Sb-terminated (1×3) phase found at typical Sb2 fluxes used during heterostructure growth.
Asymmetric Hybrid Al(Ga)SbAs/InAs/Cd(Mg)Se Heterostructures for Mid-IR LEDS and Lasers
Authors: Ivanov S. V. , Kaygorodov V. A. , Solov'ev V. A. , Ivanov E. V. , Moiseev K. D. , Sorokin S. V. , Meltzer B. Ya. , Semenov A. N. , Mikhailova M. P. , Yakovlev Yu. P. , Kop'ev P. S. 
Published: April 2011

AbstractA hybrid double heterostructure with large asymmetric band offsets, combining AlAsSb/InAs (as a III–V part) and CdMgSe/CdSe (as a II–VI part), has been proposed as a basic element of a mid-infrared laser structure design. The p-i-n diode structure has been successfully grown by molecular beam epitaxy (MBE) and exhibited an intense long-wavelength electroluminescence at 3.12 μm (300K). A II–VI MBE growth initiation with a thin ZnTe buffer layer prior to the CdMgSe deposition results in a dramatic reduction of defect density originating at the II–VI/III–V interface, as demonstrated by transmission electron microscopy. A less than 10 times reduction of electroluminescence intensity from 77 to 300K indicates an efficient carrier confinement in the InAs active layer due to high potential barriers in conduction and valence bands, estimated as ΔEC = 1.28 eV and ΔEV ∼ 1.6 eV. An increase in the pumping current results in a super-linear raising the EL intensity. The type of band line up at the coherent InAs/Cd1−xMgxSe interface is discussed for 0≤x≤0.2, using experimental data and theoretical estimations within a model-solid theory.
Airplane and Drop Experiments on Crystallization of InxGa1-xSb Semiconductor under Different Gravity Conditions
Authors: Balakrishnan Krishnan , Hayakawa Yasuhiro , Komatsu Hideki , Murakami Noriaki , Nakamura Tetsuo , Kimura Tadashi , Ozawa Tetsuo , Okano Yasunori , Miyazawa Masafumi , Dost Sadik , Dao Le. H. , Kumagawa Masashi 
Published: April 2011

AbstractMelting and crystallization experiments of InGaSb were done under the reduced gravity condition (10–2G) in an airplane and at the normal gravity condition (1G) in the laboratory. Crystallized InGaSb was found to contain many needle crystals in both the cases. Reduced gravity condition was found to be more conducive for crystal growth than the normal gravity condition. Formation of spherical projections on the surface of InGaSb during its crystallization was in-situ observed using a high speed CCD camera in the drop experiment. Spherical projections showed dependence of gravity during its growth. Indium compositions in the spherical projections were found to vary depending on the temperature.
Characterization of LiInS2 and LiInSe2 single crystals for nonlinear optical applications
Authors: Isaenko Ludmila , Yelisseyev Alexander , Lobanov Sergei , Panich Alexander , Vedenyapin Vitaly , Smirnova Julia , Petrov Valentin , Zondy Jean-Jacques , Knippels Guido 
Published: April 2011

AbstractX-ray structural analysis, nuclear magnetic resonance, optical spectroscopy and second harmonic generation were used to characterize the new nonlinear crystals LiInS2 and LiInSe2 which possess maximum band gap (3.59 and 2.86 eV at 300 K, respectively) among ternary chalcogenides. As grown crystals are only slightly colored while color change after annealing is due to native point defects.
Transmission Characterization of Drilled Alternating-Layer Three-Dimensional Photonic Crystals
Authors: Kuramochi Eiichi , Notomi Masaya , Yokohama Itaru , Takahashi Jun-ichi , Takahashi Chiharu , Kawashima Takayuki , Kawakami Shojiro 
Published: April 2011

AbstractWe propose a new three-dimensional photonic crystal structure or drilled alternating-layer photonic crystal (DALPC), which can be fabricated by a combination of the deposition of alternating layers of dielectric films and one-time dry etching. Our band calculation predicts that the DALPC has a photonic band gap (PBG) in all directions. We fabricated a Si/SiO2DALPC by electron beam lithography, bias sputtering, and fluoride-gas electron cyclotron resonance etching. We measured the light transmission of the DALPC sample in both the in-plane and vertical directions. We observed a transmission minimum around the 1.4-μm-wavelength for all measured directions and TE/TM polarizations, which demonstrated a potential of the DALPC as a three-dimensional PBG material.
Interference lithography for 3D photonic band gap crystal layer by layer fabrication
Authors: Feigel A , Kotler Z. , Sfez B. , Arsh A. , Klebanov M. , Lyubin V. 
Published: April 2011

AbstractWe present fabrication of 3D photonic band gap woodpile crystals from photosensitive chalcogenide glass with the help of interference lithography and layer by layer construction. The alignment method is described, which is scalable to extremely small feature sizes required for photonic crystals in the visible region.
Two Dimensional Photonic Crystal Modes and Resonances in Three-dimensional Structures
Authors: Fan Shanhui , Joannopoulos J. D. 
Published: April 2011

AbstractWe present three-dimensional analysis of two-dimensional guided resonances in photonic crystal slab structures. This analysis leads to a new understanding of the complex spectral properties of such systems. Specifically, we calculate the dispersion diagrams, the modal patterns, and transmission and reflection spectra of these resonances. From these calculations, a key observation emerges involving the presence of two temporal pathways for transmission and reflection processes. Using this insight, we introduce a general physical model that explains the essential features of complex spectral properties. Finally, we show that the quality factors of these resonances are strongly influenced by the symmetry of the modes, and the strength of the index modulation.
Artificial Second Order Non-Linearity in Photonic Crystals
Authors: Feigel A , Kotler Z. , Sfez B. 
Published: April 2011

AbstractWe describe a technique for obtaining effective second order non-linearity χ2 in non centro-symmetric Photonic Crystal made from centro-symmetric materials (e.g. glass, Ge or Si). The effect is based on the electric quadrupole transition, strong electromagnetic mode deformation and different contributions to the volume polarization from different parts of the photonic crystal1.
Profiling electric fields around dislocations in GaN
Authors: Cherns D. , Jiao C.G. , Mokhtari H. 
Published: April 2011

AbstractElectron holography has been used to measure the electric potential around edge and screw dislocations in n-GaN viewed in a near end-on geometry. It is shown that the potential at edge dislocations is 2V below that in the bulk consistent with a negative charge of 2 electrons/c (c = 0.52nm). Preliminary results, which suggest that screw dislocations are also negatively charged, are discussed.
Band Gap Shift of GaN under Uniaxial Strain Compression
Authors: Peng H. Y. , McCluskey M. D. , Gupta Y. M. , Kneissl M. , Johnson N. M. 
Published: April 2011

AbstractThe band-gap shift of GaN:Mg epilayers on (0001)-oriented sapphire was studied as a function of uniaxial strain compression along the c-axis using time-resolved, optical absorption measurements in shock wave experiments. For longitudinal stresses ranging from 4 to 14 GPa, the band gap shift is approximately 0.026 eV/GPa. Combining this result with the known behavior of wurtzite GaN under hydrostatic pressure and biaxial stress, a new set of deformation potentials has been estimated: acz-D1 = -10.2 eV, act-D2 = -7.9 eV, D3 = 1.33 eV and D4 = -0.74 eV. A slow band gap shift is also observed following the immediate band gap increase upon impact. This phenomenon can be explained by a time-dependent screening of the piezoelectric field.
Improved Mobilities and Resistivities in Modulation-Doped P-type AlGaN / GaN Superlattices
Authors: Waldron Erik L. , Graff John W. , Schubert E. Fred , Dabiran Amir M. 
Published: April 2011

AbstractP-type AlGaN / GaN superlattice structures have demonstrated higher acceptor activation due to a modulated valence band resulting from the superlattice as well as spontaneous and piezoelectric polarization fields. The polarization effects are due to the wurtzite structure of AlGaN and the strain present in AlxGa1-xN / GaN heterostructures. Variable temperature Hall effect studies of Mg doped Al0.20Ga0.80N / GaN superlattices reveal an improvement in resistivity and mobility for modulation-doped structures versus uniformly doped structures. Very low resistivities less than 0.1 & cm and hole mobilities ~ 36 cm2/V s are demonstrated. This improvement is attributed to a reduction of neutral and ionized impurity scattering for the two-dimensional hole gas present in the GaN layers of the modulation-doped superlattice. The improvement is greatest at temperatures below ~ 150 K. The doped regions of the superlattices have Mg concentrations of ~1019 cm-3. Two modulation-doped samples were grown by MBE: a standard scheme with dopants only in the AlGaN barriers, and a shifted scheme with dopants concentrated near the AlGaN / GaN interfaces. The standard sample has mobilities of 8.9 and 36 cm2/V s at 300 and 90 K, respectively. Resistivities of the standard sample are 0.21 and 0.068 Ω cm at 300 and 90 K, respectively. Carrier concentrations for this sample are 3.4 and 2.5 x 1018 cm-3 at 300 and 90 K, respectively. Capacitance-voltage profiling on the samples shows a clear indication of a two-dimensional hole gas as well as the periodicity of the superlattice.
High Efficiency UV-Emission at 345 nm from InAlGaN Light-Emitting Diodes
Authors: Kinoshita A. , Hirayama H. , Ainoya M. , Yamabi T. , Hirata A. , Aoyagi Y. 
Published: April 2011

AbstractOptical and electrical properties of 340 nm-band bright UV-light emitting diodes (LEDs) were compared between In0.03Al0.20Ga0.77N and other active regions. Single peaked and high efficiency ultraviolet (UV) emission at 345 nm from In0.03Al0.20Ga0.77N LEDs is achieved under continuous current injection conditions. Any significant broadening and peak shift of the electroluminescence (EL) spectrum were not observed. We attribute such a good properties to using of high quality InAlGaN-quaternary active layer. The EL intensity of the InAlGaN quaternary-based LED showed more one order of magnitude higher intensity than that of AlGaN and GaN based LEDs. Additionally, The I-L characteristics of the InAlGaN quaternary-based LED showed a linearly increasing of intensity with increasing of injection current density, that is also observed for InGaN based LEDs. This shows the recombination efficiency of the InAlGaN-based LED is as much as that of InGaN based LEDs. From these results InAlGaN quaternary is expected to be a promising material for UV LEDs and LDs.
Growth of GaN epilayers on Si(111) substrates using multiple buffer layers
Authors: Hageman P.R. , Haffouz S. , Grzegorczk A. , Kirilyuk V. , Larsen P.K. 
Published: April 2011

AbstractWe present a study of the growth of high quality GaN films on Si(111) substrates by MetalOrganic Chemical Vapor Deposition technique. In order to improve the quality of the epitaxial films we introduced different nucleation or buffer layers and combinations of them. Our results obtained on an optimized AlN nucleation layer will serve as reference point. In order to improve the quality of the epitaxial films we introduced different combinations of nucleation and intermediate layers. The first combination consists of an optimized AlN nucleation layer followed by a 1 m-thick GaN film, on which we deposited SixNy/GaN intermediate layers. Based on the optimized AlN nucleation layer, we introduced AlGaN/GaN superlattices or AlN intermediate buffer layers. Additionally, we present results on the modification the Si(111) surface with NH3 to promote nucleation from selective GaN islands. In all experiments the total thickness of the GaN epilayers was 3 m m. X-ray diffraction, photoluminescence, Hall measurements and atomic force microscopy were used in order to elucidate the effectiveness of these growth processes. For the most successful deposition scheme, the one with the SixNy/GaN intermediate layers, the resulting GaN layers are of high quality as compared to the other methods. The donor bound exciton, which dominates the photoluminescence spectrum, showed a full width at half maximum (FWHM) of about 50 meV at room temperature and 10 meV at 4K. The FWHM of the symmetric (0002) rocking curves in w-scan is about 640 arcsec. The root-mean-square roughness, as measured by atomic force microscopy, does not exceed 10 Å.
V - III ratio effect on Cubic GaN Grown by RF Plasma Assisted Gas Source MBE
Authors: Sung Li-Wei , Lin Hao-Hsiung , Chia Chih-Ta 
Published: April 2011

AbstractWe report the investigation on the growth conditions and optical properties of cubic GaN films grown on (001) GaAs substrate by using RF plasma assisted gas source MBE. The cubic GaN films were deposited at different Ga to N flux ratios that were determined by deposition rates directly. Three growth regimes, namely, Ga droplet, intermediate Ga stable, and N stable regime, are defined in the growth diagram. Optical quality of these films was determined by using photoluminescence (PL). Micro-Raman scattering were performed to analyze the crystallinity of the films. Optimal growth condition of cubic GaN is on the boundary of intermediate Ga stable regime and Ga droplet regime at a growth temperature of Ts = 720°C.
Electroluminescence And Photoluminescence Studies Of A Nitride-Rich GaN1-XPx SQW Structure LED Grown By Laser-Assisted Metal-Organic Chemical Vapor Deposition
Authors: Kikawa Junjiroh , Yoshida Seikoh , Itoh Yoshiteru 
Published: April 2011

AbstractWe fabricated a light-emitting diode (LED) having a nitride-rich GaN1-xPx single quantum well (SQW) structure grown using laser-assisted metal-organic chemical vapor deposition (LA-MOCVD). The peak energy of the electroluminescence (EL) of the LED was 2.88 eV, which is in the vicinity of the energy due to the recombination of the bounding exciton by P atoms, known as an isoelectronic trap in GaN. We observed a blue shift of this peak by increasing the drive current. We also observed extra emission of band-to-band recombination at about 3.4 eV above a drive current of 32 mA, where the external quantum efficiency was already saturated.
Light emitters fabricated on bulk GaN substrates. Challenges and achievements.
Authors: Perlin Piotr , ski M. Leszczy , Prystawko P. , Czernecki R. , Nowak G. , Wisniewski P. , Dmowski L. , Teisseyre H. , Litwin-Staszewska E. , Suski T. , Grzegory I. , Porowski S. , Ivanov V.Yu. , Godlewski M. , Holst J. , Hoffman A. 
Published: April 2011

AbstractWe used high-pressure grown GaN single crystal substrates to fabricate dislocation free optoelectronic devices like light emitting diodes and laser diodes structures. The latter ones demonstrated laser action under optical pumping condition with the threshold of about 200 kW/cm2 at room temperature. In the present paper we would focus on the specific aspects of the homoepitaxial growth by MOVPE method including epi-ready substrate preparation and surface polarity choice. We believe that our results demonstrate clearly the feasibility of device fabrication based on high-pressure grown GaN bulk crystals.
Superior Structural Quality of Newly Developed GaN Pendeo-Epitaxial Layers.
Authors: Liliental-Weber Z. , Jasinski J. , Cherns D. , Baines M. , Davis R. 
Published: April 2011

AbstractTransmission electron microscopy of plan-view and cross-section samples of pendeo-epitaxial layers is described. Samples grown with and without silicon nitride masks are compared. A large misorientation of the GaN grown above the mask was observed, with 2-3° tilt between wing and seed areas, caused by additional nucleation on the mask layer. Some misorientation was also observed between wing/wing areas of the sample. Samples grown without silicon nitride masks show much smaller misorientations and contain different types of defects.
Compositional and structural studies of amorphous GaN grown by ion-assisted deposition
Authors: Lanke U. D. , Koo A. , Ruck B. J. , Lee H. K. , Markwitz A. , Kennedy V. J. , Ariza M. J. , Jones D. J. , Rozière J. , Bittar A. , Trodahl H. J. 
Published: April 2011

AbstractAmorphous GaN films have been deposited onto various substrates by ion-assisted deposition. The films were deposited at room temperature using nitrogen ion energies in the range 40-900 eV. Rutherford backscattering spectroscopy and nuclear reaction analysis show that the Ga:N atomic ratio is approximately one for films grown with ion energy near 500 eV; these films have the highest transparency. Films grown with ion energies below 300 eV are Ga rich, and show reduced transparency across the visible. Raman spectroscopy, x-ray diffraction, and transmission electron microscopy confirm the amorphous nature of the films. Annealing studies on a-GaN establish that the films begin to crystallise at a temperature of about 700 C. To investigate the local bonding environment of the Ga or N atoms, we have measured the extended x-ray absorption fine structure (EXAFS) of the transparent GaN films. The EXAFS results indicate that the films are dominated by heteropolar tetrahedral bonding, with a low density of homopolar bonds.
Study of High Nitrogen Compositions GaNAs and GaInNAs Material Quality by X-ray Diffraction and Photoluminescence
Authors: Ng T. K. , Yoon S. F. , Wang S. Z. , Loke W. K. , Fan W. J. 
Published: April 2011

AbstractGaNAs and GaInNAs growths are subjects of considerable interest due to its technological importance in long wavelength lasers emitting within the optical-fiber communication wavelength window (1.31 – 1.55 m m). We study GaNAs and GaInNAs materials growth on (100) semi-insulating GaAs substrate with high nitrogen compositions (>2%) using a solid source molecular beam epitaxy (SSMBE) system in conjunction with a RF plasma source. GaNAs layer with high nitrogen compositions of 4.85% and 6% with good XRD peak intensities were successfully grown. GaInNAs quantum wells (QWs) were then grown with reference to the nitrogen compositions measured in the GaNAs materials to obtain nitrogen compositions > 2%. The photoluminescence (PL) peak positions of the GaInNAs QWs blueshifted after annealing at 840°C and 10min. It was found that the blueshift of PL peaks are highly dependent on nitrogen compositions.
Similarities in the Optical Properties of Hexagonal and Cubic InGaN Quantum Wells
Authors: Chichibu S. F. , Sugiyama M. , Onuma T. , Kuroda T. , Tackeuchi A. , Sota T. , Kitamura T. , Nakanishi H. , Ishida Y. , Okumura H. , Keller S. , Mishra U. K. , DenBaars S. P. , Nakamura S. 
Published: April 2011

AbstractOptical properties of fully-strained wurtzite and zincblende InxGa1-xN/GaN multiple quantum well (MQW) structures were compared to discuss the origin of exciton localization. In contrast to the hexagonal InGaN MQWs, the photoluminescence (PL) peak energy of cubic InGaN MQWs showed a moderate blueshift with decreasing well thickness, L, and low-temperature PL decay time of the cubic MQWs did not depend strongly on L. The results imply that the wavefunction overlap in cubic InGaN MQWs was not reduced compared to the hexagonal ones, since they do not suffer from the electric field normal to the QW plane due either to spontaneous or piezoelectric polarization. Both MQWs exhibited a large and composition-dependent bandgap bowing, and time-resolved PL (TR-PL) signals showed a stretched-exponential decay even at room temperature. The exciton localization is considered to be an intrinsic property of InGaN.
Characterization of high-quality epitaxial AlN films grown by MOVPE
Authors: Shibata Tomohiko , Asai Keiichiro , Nagai Teruyo , Sumiya Shigeaki , Tanaka Mitsuhiro , Oda Osamu , Miyake Hideto , Hiramatsu Kazumasa 
Published: April 2011

AbstractThis paper presents the correlation between overall crystal mosaicities and dislocation behaviors of high-quality AlN epitaxial films grown on a C-plane sapphire substrate using a low-pressure metal organic vapor phase epitaxy (LP-MOVPE) method. Typical full width at half maximum (FWHM) values of x-ray rocking curves (XRC) for (0002) and (10-10) of the AlN are 80arcsec and 1800arcsec, respectively. From transmission electron microscopy (TEM) observations, edge-type dislocations thread the AlN layer, however, almost all screw-type dislocations disappear at an early AlN growth stage. The dislocation density of the AlN films in its surface region is as low as approximately 1x1010 cm-2. The distribution of the dislocations is considered to be caused by a large twisted mosaicity and a very small tilted mosaicity.
Helical-Type Surface Defects in GaN and InGaN Thin Films Epitaxially Grown on GaN Templates at Reduced Temperatures
Authors: Miraglia Peter , Preble Edward , Roskowski Amy , Einfeldt Sven , Davis Robert F. 
Published: April 2011

AbstractThe surface morphologies of GaN and InGaN films grown at 780°C by metalorganic vapor phase epitaxy were determined using atomic force microscopy. A qualitative model is presented to explain observed instabilities in the step morphology of these films, namely, the formation of hillock islands and v-defects that give rise to surface roughening. The latter are a result of a boundary dragging effect, where interactions occur between the movement of homogeneous and heterogeneous steps and the tendency to form atom clusters in the terrace in the transition in kinetic growth regime. The tendency to form v-defects was associated with dislocation density. A delay in the formation of v-defects in InGaN was observed and associated with the ammonia partial pressure and the interactions between hillock islands and pure screw or mixed dislocations. Hillock island formation was attributed to a transition in thermodynamic mode to three-dimensional island growth. Explanations for the foregoing observations are based on growth model theory previously developed by Burton, Cabrera, and Frank (BCF) and on changes in the surface kinetics with temperature, In composition, and gas phase composition.
Effect of Crystalization On Photoluminescence of ER2O3 Thin Films
Authors: Duan Xiaoman , Saini Sajan , Chen Keven , Lipson Michel , Michel Jurgen , Kimerling Lionel C. 
Published: April 2011

AbstractThe effect of microstructures on the photoluminescence of Er2O3thin films has been systematically studied in this paper. The Er2O3 film was fabricated via reactive sputtering of Er metal in an Ar/O2 atmosphere. The as-deposited thin film contained both amorphous and polycrystalline structures, which showed weak photoluminescence at 1.55 µm. Annealing at an elevated temperature from 650 to 1050 °C in O2 ambient significantly incorporated oxygen into the lattice and strongly promoted crystalline grain growth, which in turn dramatically induced the transaction of photoluminescence from 1.55 µm to 1.541 µm. The ideal large crystal Er2O3 structure with fcc-Er2O3 and bcc-Er2O3 precipitates was obtained by conducting a two-step annealing (650 °C for 5 hours followed by 1020 °C for 2 hours) which resulted in a sharp photoluminescence peak at 1.541 µm. Further significant enhancement of PL at 1.541 µm was achieved via RTA at 1050 °C for 30 seconds to introduce more fcc-Er2O3 precipitates into the bcc-Er2O3 matrix.