bluuebunny/crossref_metadata_2025_split huggingface dataset:
Process Development and Reliability Study Of Gfpdni Finish For Sc Packaging
Authors: Boguslavsky I. , Abys J. A. 
Published: April 2011

AbstractGFPdNi was tested for Frame-Lid Assemblies (FLAs) utilized in the sealing SC packages. Plating conditions were adjusted to enhance corrosion resistance with concurrent control over hydrogen content and thickness distribution of the deposit. GFPdNi-plated lids exhibit excellent corrosion resistance, most notably when compared standard Au-plated and GFPdNi-plated lids after a heat-treatment used to simulate sealing process (Fig. 1). This is most likely due to PdNi layer being known as a good interdiffusion barrier.The reliability of lidded packages was tested by standard methods. It has been revealed that the thickness of the PdNi layer affects the yield in thermal cycling and thermal shock experiments. Auger studies implemented for failure analysis showed the correlation between intermetallic diffusion during the sealing process (due to insufficient thickness of PdNi deposit) and the reliability of the solder joint. A successful field evaluation trial has proven the capability of this new plating process.
Patterning of LiGaO2 and LiAlO2 by Wet and Dry Etching
Authors: Lee J. W. , Pearton S. J. , Abernathy C. R. , Wilson R. G. , Chai B. L. , Ren F. , Zavada J. M. 
Published: April 2011

ABSTRACTLiGaO2 and LiAlO2 have similar lattice constants to GaN, and may prove useful as substrates for III-nitride epitaxy. We have found that these materials may be wet chemically etched in a number of acid solutions, including HF, at rates between 150–40,000 Å/min. Dry etching with SF6/Ar plasmas provides faster rates than Cl2/Ar or CH4/H2/Ar under Electron Cyclotron Resonance conditions, indicating the fluoride etch products are more volatile that their chloride or metalorganic/hydride counterparts. Dry etch rates are low ( < 2, 000 Å/min), providing high selectivity (>5) over the nitrides. The incorporation of hydrogen in these materials is also of interest because this could provide a reservoir of hydrogen that may passivate dopants in overlying nitride films. In 2H implanted samples, 50 % of the deuterium is lost by evolution from the surface by annealing at 400 °C for 20 min and all of the deuterium is gone at 700°C. The diffusivity of 2H is ∼10-13 cm2/s at 250°C in LiA1O2, approximately two orders of magnitude higher than in LiGaO2.
Ohmic Contact to n-GaN with TiN Diffusion Barrier
Authors: Kamińska E. , Piotrowska A. , Guziewicz M. , Kasjaniuk S. , Barcz A. , Dynowska E. , Bremser M. D. , Nam O. H. , Davis R. F. 
Published: April 2011

ABSTRACTThe formation of n-GaN/Ti ohmic contacts with TiN diffusion barriers has been investigated by electrical measurements, x-ray diffraction and SIMS. It has been shown that the onset of the ohmic behaviour is associated with the thermally induced phase transformation of Ti into TiN at the GaN/Ti interface. It is suggested that the process is accompanied by an increase in the doping level in the semiconductor subcontact region. The presence of a TiN barrier is found to inhibit excessive decomposition of GaN and to confine the reaction between n-GaN and Ti.
PtIn2 ohmic contacts to n-GaN
Authors: Ingerly D. B. , Chang Y. A. , Perkins N. R. , Kuech T. F. 
Published: April 2011

ABSTRACTA new metallization scheme has been developed to form ohmic contacts to n-GaN. Contacts were fabricated by sputtering the intermetallic compound, PtIn2 on n-GaN (n ∼ 5 ×l017 cm−3) grown by metalorganic vapor phase epitaxy (MOVPE) with some of the contacts subjected to rapid thermal annealing. Contacts in the as-deposited state exhibited nearly ohmic behavior with a specific contact resistance of 1.2 × 10−2 Ω cm2. Contacts subjected to rapid thermal annealing at 800 °C for 1 minute exhibited linear current-voltage characteristics and a decrease in contact resistance. To rationalize the reaction at the contact interface the phase diagram of the PtIn2-PtGa2-InN-GaN reciprocal system at 800 °C was calculated based on known and estimated thermodynamic values. This phase diagram suggests that there will be a solid state exchange of In and Ga atoms at the Ptln2/GaN contact interface producing (InxGa1-x)N and Pt(In,Ga)2. Results from Auger depth profiling used to examine the Ptln2/n-GaN contacts are consistent with this estimated phase diagram information. It is proposed that the formation of (InxGa1-x)N at the contact interface is responsible for the ohmic behavior of Ptln2 contacts.
Stacked InGaN/AlGaN Double Heterostructures
Authors: Roberts J. C. , McIntosh F. G. , Aumer M. E. , Piner E. L. , Joshkin V. A. , Liu S. , El-Masry N. A. , Bedair S. M. 
Published: April 2011

ABSTRACTInGaN ternary alloys can be the basis for light emission from the near UV to the red region of the electromagnetic spectrum. When InGaN/AIGaN double heterostructures emitting different colors are stacked in a single structure, simultaneous emission of different wavelengths will be achieved. If the color and the intensity of emission for each well are adjusted properly, tailored emission spectra, including white light, will be feasible. We demonstrate this concept with two wells emitting at different wavelengths that are stacked between AIGaN barrier layers. The emitted PL spectra for the stacked structure is found to be the superposition of the emission from the individual double heterostructures that were grown separately.
Carrier Recombination Dynamics of InGaN/GaN LEDs and Its Applications to the Optimization of uv Generation Efficiency
Authors: Basrur J. P. , Choa F. S. , Liu P-L. , Sipior J. , Rao G. , Carter G. M. , Chen Y. J. 
Published: April 2011

ABSTRACTTo obtain small size high speed ultraviolet sources, we studied the UV generation process and efficiency of GaN Blue LEDs. The blue and UV emissions follow a 4-level recombination model. Depending on a given pump pulse amplitude the UV to blue generation ratio increases and saturates with the increasing of pump pulse duration. High efficiency, upto 450 μ W UV power at 380 nm, can be obtained from a 1.2 mW blue LED.
Surface Reconstructions and III-V Stoichiometry: The Case of Cubic and Hexagonal GaN
Authors: Feuillet G. , Hacke P. , Okumura H. , Hamaguchi H. , Ohta K. , Balakrishnan K. , Yoshida S. 
Published: April 2011

ABSTRACTSurface reconstructions for MBE grown GaN are identified. Different cases are considered according to the type of substrate or crystal symmetry and surface phase diagrams are obtained. Through different examples, it is shown how growth monitoring can be efficiently achieved through the use of surface reconstructions. Finally, from the observation that a residual arsenic overpressure in the MBE chamber changes the surface reconstructions of cubic (001) GaN grown onto 3C-SiC (001) substrates to that commonly observed for GaN growth on (001) GaAs, it is proposed that arsenic might be a surfactant for nitride growth.
Low-Temperature Deposition and Characterization of AlxIn1-xN Thin Films
Authors: Qiu Guohua , Olowolafe J. O. , Peng Tao , Unruh K. M. , Swann C. P. , Piprek J. 
Published: April 2011

ABSTRACTThin III-V nitride semiconductors fidms are commonly prepared using metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). These methods often require high temperatures (800–1000°C) for the films to grow epitaxially. In the present work, we deposited AlxIn1-xN films on Si substrates by reactive magnetron sputttering method at low substrate temperature. The properties of the films have been studied by RBS, x-ray diffraction, and optical measurements. The AlxIn1-xN films deposited at room temperature were confirmed to be crystalline by x-ray diffraction. Band gap energies of our AlxIn1-xN alloys varies from 1.9 ev to 4.2 ev The bandgap energy vs. lattice constant curve was constructed and confirmed to bow downwards.
Growth of Bulk AlN and GaN Single Crystals by Sublimation
Authors: Balkas C. M. , Sitar Z. , Zheleva T. , Bergman L. , Shmagin I. K. , Muth J. F. , Kolbas R. , Nemanich R. , Davis R. F. 
Published: April 2011

ABSTRACTSingle crystals of A1N to 1 mm thickness were grown in the range 1950-2250°C on 10×10 mm2 α(6H)-SiC(0001) substrates via sublimation-recondensation method. Hot pressed polycrystalline AlN was used as the source material. The color varied from transparent to dark green/blue. The crystal morphology varied with growth conditions. Most crystals were 0.3 mm -1 mm thick transparent layers which completely covered the substrates. Raman, optical and transmission electron microscopy (TEM) results are presented. Single crystals of gallium nitride (GaN) were also grown by subliming powders of this material under an ammonia (NH3) flow. Optical microscopy, Raman and photoluminescence results are shown.
Structural Analysis of GaN and GaN/InGaN/GaN DH Structures on Sapphire (0001) Substrate Grown by MOCVD
Authors: Sato Hisao , Naoi Yoshiki , Sakai Shiro 
Published: April 2011

ABSTRACTWe have investigated lattice structures of GaN and InGaN/GaN single-heterostructures (SH) and double-heterostructures (DH) by the reciprocal space mapping using X-ray diffraction technique from (0002) plane. For a single GaN layers, the transition of the film structure from grains with relatively independent orientation at about 0.3 μm followed by the coalescence at about 1 μm, to a uniform film with mosaic structure at 1.4 μm was clearly observed. For DH structure, ω-mode FWHMs both from InGaN (In composition approximately 7 %) and capping-GaN layers increased with increasing film thickness from 20 nm to 110 nm indicating the increased mosaic structure in the thick InGaN. We also observed the dislocation related to this increasing mosaic structure.
Hexagonal Growth Hillocks in GaN Epilayers
Authors: Middleton P. G. , Trager-Cowan C. , Mohammed A. , O’Donnell K. P. , Van Der Stricht W. , Moerman I. , Demeester P. 
Published: April 2011

ABSTRACTWe describe a study of the hexagonal growth hillocks commonly present in gallium nitride films. The MOVPE-grown epilayers of the present work exhibit a predominantly smooth morphology but small groups of hexagonal hillocks were found to populate the surface, particularly at the sample edges.Scanning electron (SE) micrographs were taken of several groups of hillocks. At the maximum beam energy of 25 keV, two types of hexagonal hillock are visible. Hillocks in the first group are terminated by an apex (ie. they are pyramidal in form), while the other, flat-topped, hillocks terminate on (0001)-facets. As one lowers the electron beam energy, thereby reducing beam penetration, some of the flat-topped hillocks disappear from the image. From this we tentatively deduce that these hillocks are buried. The result of further investigations, using an atomic force microscope, are consistent with the presence of sub-surface features.The relationship between the luminescence and morphological properties of a pyramidal hillock is studied via cathodoluminescence imaging. The band-edge emission originates from the full hexagonal structure, except for the central region, where only the defect-related yellow luminescence is apparent. We suggest this might be explained by defects associated with inversion domain boundaries at the hillock centre.
Recombination of Localized Excitons in InGaN Single- and Multiquantum-Well Structures
Authors: Chichibu S. , Azuhata T. , Sota T. , Nakamura S. 
Published: April 2011

ABSTRACTSpontaneous emission mechanisms of InGaN single quantum well (SQW) blue and green light emitting diodes (LEDs) and multiquantum well (MQW) laser diode (LD) structures were investigated. Their static electroluminescence (EL) peak was assigned to the recombination of excitons localized at certain potential minima in the quantum well (QW). The transmission electron micrographs (TEM) indicated fluctuation of In molar fraction in the QWs. The blueshift of the EL peak caused by the increase of the driving current was explained by combined effects of the quantum-confinement Stark effect and band filling of the localized states by excitons.
AlxGa1-xN-Based Materials and Heterostructures
Authors: Kung P. , Saxler A. , Walker D. , Zhang X. , Lavado R. , Kim K.S. , Razeghi M. 
Published: April 2011

ABSTRACTWe present the metalorganic chemical vapor deposition growth, n-type and p-type doping and characterization of AlxGa1-xN alloys on sapphire substrates. We report the fabrication of Bragg reflectors and the demonstration of two dimensional electron gas structures using AlxGa1-xN high quality films. We report the structural characterization of the AlxGa1-xN / GaN multilayer structures and superlattices through X-ray diffraction and transmission electron microscopy. A density of screw and mixed threading dislocations as low as 107 cm-2 was estimated in AlxGa1-xN / GaN structures. The realization of AlxGa1-xN based UV photodetectors with tailored cut-off wavelengths from 365 to 200 nm are presented.
Changes in Optical Transmittance of Aluminum Nitride thin Films Exposed to Air
Authors: Sakuragi Yoshifumi , Watanabe Yoshihisa , Nakamura Yoshikazu , Amamoto Yoshiki 
Published: April 2011

ABSTRACTAluminum nitride (AlN) thin films have been synthesized by ion-beam assisted deposition method and the influence of air-exposure on the optical transmittance has been studied. The kinetic energy of nitrogen ion beam was kept at 0.1 or 1.5 keV under the constant current density. Synthesized films have been exposed to controlled air (23 °C and RH; 50%) and optical transmission spectrum from 190 to 2200 nm has been measured by UV-visible spectrometer every week. Surface morphology of the films has been observed with an optical microscope (OM). The optical transmittance has not changed drastically up to one year. Observations by OM show that round features of some microns were produced on the surface after about 25 weeks exposure. These substances seem to be reaction products between AlN and water in air.
Optical Studies of MOCVD InxGa1-xN Alloys
Authors: Little B.D. , Shan W. , Song J.J. , Feng Z.C. , Schurman M. , Stall R.A. 
Published: April 2011

ABSTRACTWe present the results of optical studies of InxGa1-xN alloys (0<x<0.2) grown by metalorganic chemical vapor deposition on top of thick GaN epitaxial layers with sapphire as substrates. Photoluminescence (PL) and photoreflectance (PR) measurements were performed at various temperatures to determine the band gap and its variation as a function of temperature for samples with different indium concentrations. Carrier recombination dynamics in the alloy samples were studied using time-resolved luminescence spectroscopy. While the measured decay time for the alloy near-band-edge PL emissions was observed to be generally around a few hundred picoseconds at 10 K, it was found that the decay time decreased rapidly as the sample temperatures increased. This indicates a strong influence of temperature on the processes of trapping and recombination of excited carriers at impurities and defects in the InGaN alloys.
Strain Effects on Excitonic Transitions in GaN
Authors: Shan W. , Hauenstein R.J. , Fischer A.J. , Song J.J. , Perry W.G. , Bremser M.D. , Davis R.F. , Goldenberg B. 
Published: April 2011

ABSTRACTWe present the results of experimental studies of the strain effects on the excitonic transitions in GaN epitaxial layers on sapphire and SiC substrates. Photoluminescence and reflectance spectroscopies were performed to measure the energy positions of exciton transitions and X-ray diffraction measurements were conducted to examine the lattice parameters of GaN epitaxial layers grown on different substrates. Residual strain induced by the mismatch of lattice constants and thermal-expansion between GaN epitaxial layers and substrates was found to have a strong influence in determining the energies of excitonic transitions. The overall effects of the strain generated in GaN is compressive for GaN grown on sapphire and tensile for GaN on SiC substrate. The uniaxial and hydrostatic deformation potentials of wurtzite GaN were derived from the experimental results. Our results yield the uniaxial deformation potentials b1≈−5.3 eV and b2≈2.7 eV, as well as the hydrostatic components a1≈−6.5 eV and a2≈−11.8 eV.
Investigation of Vacancies in GaN by Positron Annihilation
Authors: JØrgensen L. V. , Kruseman A. C. , Schut H. , Van Veen A. , Fanciulli M. , Moustakas T. D. 
Published: April 2011

ABSTRACTPositron beam analysis has been performed on autodoped n-type, semi-insulating and Mg doped p-type epitaxially grown layers of GaN on sapphire. Doppler Broadening measurements clearly indicate the presence of vacancies in the intrinsically autodoped n-type GaN by an increase in the annihilation Doppler lineshape S-parameter of 1.04 relative to the value for the high resistivity sample. This value is typical for vacancy-type defects in compound semiconductors such as GaAs. Results of experiments with higher sensitivity to core-electrons are also presented. These two detector coincidence measurements yield information on the chemical environment surrounding the vacancies. The results are consistent with the presence of Ga vacancies in the autodoped n-type sample.
The Structure and Texture of Y2O3:Tb Nanocrystals
Authors: Taylor J. , Libera M. , Goldburt E. , Bhargava R. 
Published: April 2011

AbstractThis paper presents the results of microstructural studies of terbium-doped yttria quantum nanocrystals by imaging and diffraction in a transmission electron microscope. The nanocrystals are typically found in clusters of varying size. Electron energy-loss spectroscopy confirms that the particles consist of yttrium and oxygen. Analysis of selected-area electron diffraction patterns shows that the nanocrystals largely have the cubic structure found in bulk yttria. These patterns furthermore suggest that within each cluster the nanocrystals align themselves with a preferred orientation relative to the incident electron beam as well as to each other.
Characterization of Light Emitting Porous Polycrystalline Silicon Films
Authors: Poon M. C. , Han P. G. , Sin J. K. O. , Wong H. , Ko P. K. 
Published: April 2011

AbstractPolycrystalline silicon (poly-Si) thin films (∼700nm) were deposited by LPCVD, doped with 950°C phosphorous diffusion, and rendered porous by anodization and stain etching. From x-ray photoelectron spectroscopy, poly-Si films have atomic concentration of C(ls):0(ls):Si(2p) = 6%:15%:79%. However, porous poly-Si (PPS) films with weak photoluminescence (PL) have C:O:Si of 20%:38%:42%. For PPS films with strong PL, C:O:Si is 11%:38%:51%. From micro-Raman, scattered spectra for 632nm laser source has peak at 735nm and full wave half maximum (FWHM) of 76nm, and is similar to the PL spectra excited by 400nm uv laser source. High resolution transmission electron microscopy (TEM) study shows that PPS film is of complex structure and composes of numerous Si nano-crystals (1∼10nm) surrounded by amorphous materials.
Tem Study of Porous Silicon Fabricated from N- and P-Type Doped Polycrystalline Films
Authors: Haji L. , Le Thomas Y. , Chane Che Lai F. , Joubert P. 
Published: April 2011

AbstractThe formation of porous silicon (PS) from n/p, n+/p and p+/n structures carried from polycrystalline silicon films (poly-Si) deposited on single crystal silicon (c-Si) substrates was studied by cross-sectional transmission electron microscopy. Our results clearly show that the pore formation in such structures involve the extended defects of the poly-Si film. The role played by these defects depends on the doping type and level, and on whether the anodization is performed under illumination or not.
Optical Sensors based on Porous Silicon Multilayers: a Prototype
Authors: Theiβ W. , Arens-Fischer R. , Hilbrich S. , Scheyen D. , Berger M. G. , Krüger M. , Thönissen M. 
Published: April 2011

AbstractPorous silicon multilayers are easily produced by a variation of the current density during the electrochemical etching process. The obtained porosity profile in depth is equivalent to a refractive index profile. Preparing appropriate multilayer systems one can design optical filters with sharp reflectivity peaks from the infrared through the whole visible spectral range (dielectric mirrors). Stability in time is achieved applying a suitable oxidation process. In many cases of optical process and material control the required spectral decomposition of the probing light can be done with sufficient accuracy by a set of porous silicon optical filters whose spectral characteristics can lbe adapted easily to the given problem. In this work we present the prototype of an optical sensor that is a low-cost alternative to ‘real’ (and expensive) spectrometers. Application examples in the infrared and visible are given to demonstrate the sensor performance;.
Fabrication of 10-nm Gratings Using STM Chemical Vapor Deposition
Authors: Archer A. , Hetrick J. M. , Nayfeh M.H 
Published: April 2011

AbstractUsing STM assisted chemical vapor deposition (STM-CVD), we have successfully fabricated what we believe are the finest gratings to date. Our best grating consists of half-micron long evenly spaced lines which have a width of 10 nm and a 10 nm interspacing. The gratings were fabricated on passivated p-type silicon <111> using trimethylaluminum (TMA) as a precursor gas. Although the composition of the nanostructures is not exactly known at this time, we believe that the lines are partially metallic. We made some systematic investigations to optimize the resolution, including studies of the effect of tunneling current, tip speed, tip-sample biasing voltage, and the effect of formation of very fine TMA whiskers on the tip.
Enhancement of the Spontaneous Emission Rates in all Porous Silicon Optical Microcavities
Authors: Pavesi L. , Cazzanelli M. , Bisi O. 
Published: April 2011

AbstractThe emission properties of a porous silicon layer placed in an optical microcavity is investigated by photoluminescence and time resolved photoluminescence measurements. The microcavity is formed by an all porous silicon Fabry-Perot filter made by two distributed Bragg reflectors separated by a λ or λ/2 porous silicon layer. Our main findings are that the spontaneous emission spectrum is drastically modified: the linewidth is narrowed, the time decay of the emission is shortened by a factor of about 2/3 at room temperature and the peak emission intensity is increased by a factor of more than 10. These facts are caused by the redistribution of the optical modes in the microcavity due to the presence of the optical resonator and to the variation of the dielectric environment.
Real-Time Monitoring of Hydrogen Elimination Processes in Pulsed-Gas PECVD Using in Situ Mass Spectroscopy
Authors: Srinivasan Easwar , Bordeaux Jeremy S. , Parsons Gregory N. 
Published: April 2011

AbstractIn situ mass spectroscopy is used to monitor and analyze the hydrogen elimination reaction products during cyclical exposure of thin films of amorphous silicon to a flux of atomic deuterium. Mass spectroscopy results that atomic deuterium etches deposited silicon forming SiD4 and abstracts hydrogen bonded to silicon in the film to form HD. The relative signal intensities show that abstraction is the primary hydrogen elimination mechanism. The energy of activation for the abstraction reaction is obtained from the mass spectroscopy signals through a first order kinetic analysis and is found to be approximately zero, indicating that abstraction is not thermally activated.