bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Excitation Mechanism of Erbium and Ytterbium in the Quaternary Compounds InGaAsP
Authors: Wellmann Peter , Winnacker Albrecht , Pensl Gerhard 
Published: April 2011

AbstractAn efficient transfer of excitonic energy to rare earth (RE) ions is crucial for possible optoelectronic applications of RE doped semiconductors. In order to investigate the energy transfer mechanism to RE ions after optical above bandgap excitation we studied the intensity of the 4I13/2 →4 4I15/2-transition of Er3+ (1.54μm) and the one of the 2F5/2 →2F7/2 -transition of Yb3+ (lμm) (loped into InGaAsP-layers lattice matched to InP. By varying the composition of the quaternary compoun ds, the bandgap energy together with the RE bound exciton energy were tuned relative to the RE excitation energy, and the effect on the RE luminescence intensity was observed. The results can be interpreted by stating a) that the energy transfer to the RE proceeds via the RE bound exciton, and b) that the intensity of the RE luminescence is essentially determined by the rate of back transfer of the RE excitation energy ERE to the bound exciton (with excitation energy Ebe). In this back transfer the energy of the excited RE ion plus the energy of 0, 1, 2 ... L0-phonons (energy Elo) is used to reexcite the bound exciton, instead of being emitted as an RE luminescence photon. For compositions where Ebe = ERE + n. Elo (n = 0, 1, 2...) we have a maximum of back transfer and correspondingly a, minimum in RE luminescence. In between the intensity has a, maximum.
Excitation Mechanisms and Light Emitting Device Performances in Er-Doped Crystalline Si
Authors: Priolo F. , Coffa S. , Franzo G. , Polman A. 
Published: April 2011

AbstractIn this paper the performances of room temperature operating light emitting diodes (LEDs), fabricated by Er ion implantation of crystalline silicon, are investigated in detail. It is shown that 1.54 μm emission is observed under both forward and reverse bias operation, with a much higher intensity under reverse bias. The excitation mechanisms of Er3+ are demonstrated to be very different in the two cases: under forward bias Er is excited through the electron - hole recombination at an Er - related level, while under reverse bias impact excitation by hot carriers represents the excitation process. This last mechanism is shown to occur with a cross section of 6 × 10−17 cm2 and population inversion of the excitable Er sites within the depletion region is demonstrated. The efficiency and limitations of this approach are also discussed.
Properties and Growth of MBE Grown Erbium Doped Gallium Arsenide Co-Doped with Selenium
Authors: Rutter P. , Singer K. E. , Peaker A. R. , Wright A. C. 
Published: April 2011

AbstractThe growth of erbium doped GaAs by molecular beam epitaxy (MBE) can, depending on growth conditions, result in the precipitation of small spherical particles of erbium arsenide. It has been observed that by reducing the V:III (As:Ga) flux ratio to close to stoichiometry wirelike precipitates roughly aligned in the direction of growth are produced. The concentration of erbium incorporated into the GaAs lattice for a constant erbium flux is also affected by the As:Ga flux ratio with an increase in erbium doping being observed with decreasing As:Ga flux ratio.Electrical measurements have been performed on erbium doped GaAs samples co-doped with selenium, an n-type dopant. Measurements have revealed that when erbium is present, the electron concentration is reduced by an amount approximately equal to 70% of the erbium concentration. DLTS measurements have shown that although large concentrations of deep levels are present in erbium doped material, the measured concentration of these deep levels is not high enough to account for the observed reduction in electron concentration with erbium doping.
Properties of Ion Implanted and UHV-CVD Grown Si:Er
Authors: Morse M. , Zheng B. , Palm J. , Duan X. , Kimerling L. C. 
Published: April 2011

AbstractWe have fabricated Si:Er films by ion implantation and ultra-high vacuum chemical vapor deposition (UHV-CVD). The energy of the ion implantation was varied from 200 keV to 4.5 MeV. Oxygen was co-implanted to overlap the erbium profile. At implant energies of 400 keV, we found that the luminescence was optimized at a lower annealing temperature (800° C, 30 minutes) than that needed for the 4.5 MeV implant (900°C, 30 minutes). The light intensity per erbium atom is critically dependent on the implantation energy. However, spreading resistance measurements show that the donor activity of the implanted erbium is independent of energy. We have correlated the donor activity with quantum efficiency by varying the donor spatial distribution and concentration through post implantation heat treatments.For the UHV-CVD grown Si:Er films, two erbium metallorganic precursors, Er(TMHD)3 and Er(FOD)3. have been used for growths from 550–620°C. The thickness of the erbium layers are similar to that of implanted devices but the Er concentration of 4 × 1021/cm3 exceeded the implanted material by two orders of magnitude.
Low-Temperature Growth of Si:Er by Electron Cyclotron Resonance Pecvd Using Metal Organics
Authors: Andry P. S. , Varhue W. J. , Adams E. , Lavoie M. , Klein P. B. , Hengehold R. , Hunter J. 
Published: April 2011

AbstractEpitaxial growth of Er-doped silicon films has been performed by plasma-enhanced chemical vapor deposition at low temperature (430°C) using an electron cyclotron resonance source. The goal was to incorporate an optically active center, erbium surrounded by nitrogen, through the use of the metal organic compound tris (bis trimethyl silyl amido) erbium. Films were analyzed by Rutherford backscatter spectrometry, secondary ion mass spectroscopy and high resolution x-ray diffraction. The characteristic 1.54 μm emission was observed by photoluminescence spectroscopy. Previous attempts to incorporate the complex (ErO6) using tris (2,2,6,6-tetramethyl-3,5-heptanedionato) erbium (III) indicated that excessive interstitial carbon lowered epitaxial quality and reduced photoluminescent intensity. In this study, much of the carbon was introduced onto substitutional sites maintaining good epitaxial growth. A response surface method was employed to find the plasma growth parameters yielding the highest quality luminescent films. Luminescent intensity increased for anneals up to 600°C but decreased at higher temperatures.
Neodymium and Erbium Implanted Gan
Authors: Silkowski E. , Yeo Y. K. , Hengehold R. L. , Goldenberg B. , Pomrenke G. S. 
Published: April 2011

AbstractStrong rare earth (RE) emissions from Nd and Er implanted into MOCVD grown GaN were observed through photoluminescence (PL) with below bandgap excitation from an Ar+laser. Three well resolved manifolds of 4f lines from the crystal-field split 4F3/2 → 4I9/2, 4F3/2 → 4I11/2, and 4F3/2 → 4I13/2 transitions of Nd3+ were observed at low temperature at ˜0.98, ˜1.14, and ˜1.46 μm, respectively. The Er implanted GaN showed both the 4I13/2 → 4I15/2 Er3+ transition at ˜1.54 μm and the 4I11/2 → 4I15/2 Er3+ transition at ˜1.00 μm. The Er luminescence at ˜1.54 μm and Nd luminescence at ˜1.1 μm persisted to room temperature. Both Er and Nd implanted samples showed increasing RE3+ signal as annealing temperature increased from 700 to 1000 °C. The growth of new 4f crystal-field split-lines in the ˜1.54 μm 4I13/2 → 4I15/2 manifold as annealing temperature was increased to 1000 °C suggests multiple Er3+ radiative centers.
Incorporation of High Concentration Luminescent Er Centers in Si and Porous Si by Electroplating
Authors: Sheng Chi , Cai Yongming , Gong Dawei , Huang Darning , Liu Xiaohan , Wang Xun 
Published: April 2011

AbstractIt is found that Er could only be deposited on a Si cathode by electrolysis of near neutral ErCl3 electrolyte with a large current density. The deposited Er hydrolytic layer reacts with Si at 1200 °C to form the activated Er centers that emit a 1.533 μm photoluminescence peak at room temperature. By applying this process to porous Si, an apparent doping concentration of Er larger than 1019/cm3 in the whole porous Si layer and a strong PL intensity with little temperature quenching are achieved.
High Electric Field Breakdown of 4H-SiC PN Junction Diodes
Authors: Tin C. C. , Madangarli V. , Hu R. , Luckowski E. , Casady J. , Isaacs-Smith T. , Gradinaru G. , Sudarshan T. S. , Johnson R. W. 
Published: April 2011

AbstractWe have characterized the high electric field breakdown process of several epitaxial 4H-SiC p-n structures with oxide passivation. The breakdown voltage was found to be dependent on the size of the diode structures as well as their proximity to any structural defects. The time dependence of the breakdown process was also measured to determine the characteristics of the breakdown mechanism. This time dependence measurement provides an indication of the quality of the diode structures. Both soft and abrupt breakdown mechanisms were observed showing the influence of defects on the high field behavior of the diode structures. Measurements done with and without the use of Fluorinert fluid did not show any difference in the breakdown voltage indicating that surface flashover breakdown mechanism did not play a major role in the avalanche breakdown process.
Optimization of Reactor Geometry and Growth Conditions for GaN Halide Vapor Phase Epitaxy
Authors: Safvi S. A. , Perkins N. R. , Horton M. N. , Thon A. , Zhi D. , Kuech T. F. 
Published: April 2011

AbstractA numerical model of an experimental gallium nitride horizontal vapor phase epitaxy reactor is presented. The model predicts the flow, concentration profiles, and growth rates. The effects of flowrate variation and geometry on the growth rate, growth uniformity and crystal quality were investigated. Numerical model predictions are compared to experimentally observed values. Parasitic gas phase reactions between group III and group V sources and deposition of material on the wall are shown to lead to reduced overall growth rates and inferior crystal quality. A low ammonia concentration is correlated to deposition of polycrystalline films. An optimum HVPE growth process requires selection of reactor geometry and operating conditions to minimize parasitic reactions and wall deposition while providing a uniform reactant distribution across the substrate.
Structural Characterization of Thick Gan Films Grown by Hydride Vapor Phase Epitaxy
Authors: Romano L. T. , Molnar R. J. , Krusor B. S. , Anderson G. A. , Bour D. P. , Maki P. 
Published: April 2011

AbstractThe structural quality of GaN films grown by hydride vapor phase epitaxy (HVPE) was characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD), and atomic force microscopy (AFM). Films were grown up to 40μm on sapphire with either a GaC1 pretreatment prior to growth or on a ZnO buffer layer. Dislocation densities were found to decrease with increasing film thickness. This is attributed to the mixed nature of the defects present in the film which enabled dislocation annihilation. The thickest film had a defect density of 5×107 dislocations/cm2.
Nucleation and Growth of Oriented Diamond Films on Nickel Substrates
Authors: Yang P. C. , Liu W. , Tucker D. A. , Wolden C. A. , Davis R. F. , Glass J. T. , Prater J. T. , Sitar. Z. 
Published: April 2011

Abstract(100) and (111) oriented diamond films were grown on similarly oriented single crystal Ni substrates using a multi-step seeding and growth process.In-situreflection monitoring revealed large surface reflectivity changes upon heating of the seeded substrate in H2. The reflectivity change was attributed to the surface melting and dissolution of the seeding particles. The presence of atomic hydrogen lowered the eutectic melting point of the Ni-C compound from 1325°C to about 1100°C. It appeared that the molten Ni-C-H surface layer suppressed graphite formation, which is normally observed in diamond growth on Ni, and promoted diamond nucleation. The oriented diamond films were also obtained using non-diamond carbon seeding. Based on experimental observation, a proposed model is described to explain the nucleation mechanism from the molten Ni-C-H surface layer.
Nucleation and Growth of Gallium Nitride Films on Si and Sapphire Substrates Using Buffer Layers
Authors: Perkins N. R. , Horton M. N. , Zhi D. , Matyi R. J. , Bandic Z. Z. , McGill T. C. , Kuecht T. F. 
Published: April 2011

AbstractWe have investigated the nucleation and growth of gallium nitride (GaN) films on silicon and sapphire substrates using halide vapor phase epitaxy (HVPE). GaN growth was carried out on bare Si and sapphire surfaces, as well as on MOVPE-grown GaN buffer layers. HVPE growth on MOVPE GaN/AlN buffer layers results in lower defect densities as determined by x-ray than growth directly on sapphire. HVPE GaN films grown directly on sapphire exhibit strong near-edge photoluminescence, a pronounced lack of deep level-based luminescence, and x-ray FWHM values of 16 arcsec by an x-ray θ-2θ scan. The crystallinity of GaN films on sapphire is dominated by the presence of rotational misorientation domains, as measured by xray ω-scan diffractometry, which tend to decrease with increasing thickness or with the use of a homoepitaxial MOVPE buffer layer. The effect of increasing film thickness on the defect density of the epilayer was studied. In contrast, the HVPE growth of nitride films directly on silicon is complicated by mechanisms involving the formation of silicon nitrides and oxides at the initial growth front.
Properties of Tetrahedral Amorphous Carbon Deposited by A Filtered Cathodic Vacuum ARC
Authors: Chhowalla M , Chen C W , Kleinsorge B , Robertson J , Amaratunga G A J , Milne W I 
Published: April 2011

AbstractThe properties of a highly sp3 bonded form of amorphous carbon denoted ta-C deposited from a filtered cathodic vacuum arc (FCVA) are described as a function of ion energy and deposition temperature. The sp3 fraction depends strongly on ion energy and reaches 85% at an ion energy of 100 eV. Other properties such as density and band gap vary in a similar fashion, with the optical gap reaching a maximum of 2.3 eV. These films are very smooth with area roughness of order 1 nm. The sp3 fraction falls suddenly to almost zero for deposition above about 200°C.
Chemical Beam Epitaxy Of Ganxpi- Using A N Radical Beam Source
Authors: Li N. Y. , Tomich D. H. , Wong W. S. , Solomon J. S. , Tu C. W. 
Published: April 2011

AbstractIn this study we report the growth behavior of GaNxP1−x by chemical beam epitaxy using triethylgallium, tertiarybutylphosphine, and a RF-plasma N radical beam source. We demonstrate that the N radical beam source is an effective N source for the growth of GaNxP1−x, compared to ammonia (NH3) with co-injection of phosphine (PH3) or tertiarybutylphosphine (TBP). At a growth temperature of 640°C, the N composition increases slowly from 2.5 to 2.8% even though the N2 flow rate is doubled. When the N2 flow rate is increased further, the reflection high-energy electron diffraction pattern (RHEED) becomes spotty. The N composition, however, shows a strong dependence on the growth temperature. For a fixed N plasma radical beam flux, the lower the substrate temperature is, the higher the N incorporation. The N composition can be adjusted from 0.7 to 10.2% by lowering the growth temperature from 690 to 400°C.
GaN Film Growth by a Supersonic Arcjet Plasma
Authors: Cappelli M. A. , Kull A. E. , Schwendner K. , Lee H. , Harris S. J. , Mroczkowski J. 
Published: April 2011

AbstractThis paper reports on preliminary studies of GaN growth obtained using a supersonic nitrogen arcjet plasma expanding into low pressure. A hydrogen-free and carbon-free growth environment was achieved by use of a Ga vapor source positioned downstream of the expanding plume. GaN growth rates of around 8 μm/hour were obtained in these preliminary studies. We believe these growth rates are the highest reported for a non-chemical decomposition process. The growth rates are attributed to the very high nitrogen atom fluxes estimated to be on the order of 1019 atoms/cm2/sec. The initial growth rates are believed to be well below those possible with a fully optimized system. The GaN films are characterized by Raman spectroscopy, visible-IR transmission, and x-ray diffraction. The deposited films appear to be single crystal and epitaxial on basal plane sapphire substrates.
Gan Growth By Nitrogen Ecr-Cvd Method
Authors: Chen K. H. , Chao C. H. , Chuang T. J. , Yang Y. J. , Chen L. C. , Chen C. K. , Huang Y. F. , Yang C. H. , Lin H. Y. , Chang I. M. , Chen Y. F. 
Published: April 2011

AbstractA new approach toward GaN growth using electron cyclotron resonance assisted microwave plasma enhanced chemical vapor deposition (ECR-CVD) method has been implemented. This growth technique allows for low- as well as high-temperature deposition, the use of pure nitrogen source, and a wide operating pressure that is between MOCVD and MOMBE. The unique features of this technique enable the growth of the epitaxial layer of GaN on a variety of substrates including sapphire, silicon, and LiGaO2. SEM, XRD, Raman, photoluminescence (PL), and Hall measurement are employed to characterize the deposited films. Highly oriented, (0001) textured films in the expected wurtzite structure with blue emission have been obtained.
High Temperature Surface Degradation of III-V Nitrides
Authors: Vartuli C. B. , Pearton S. J. , Abernathy C. R. , MacKenzie J. D. , Zolper J. C. , Lambers E. S. 
Published: April 2011

AbstractThe surface stoichiometry, surface morphology and electrical conductivity of AIN, GaN, InN, InGaN and InAIN was examined at rapid thermal annealing temperatures up to 1150 °C. The sheet resistance of the AIN dropped steadily with annealing, but the surface showed signs of roughening only above 1000 °C. Auger Electron Spectroscopy (AES) analysis showed little change in the surface stoichiometry even at 1150 °C. GaN root mean square (RMS) surface roughness showed an overall improvement with annealing, but the surface became pitted at 1000 °C, at which point the sheet resistance also dropped by several orders of magnitude, and AES confirmed a loss of N from the surface. The InN surface had roughened considerably even at 650 °C, and scanning electron microscopy (SEM) showed significant degradation. In contrast to the binary nitrides the sheet resistance of InAIN was found to increase by ˜ 102 from the as grown value after annealing at 800 °C and then remain constant up to 1000 °C, while that of InGaN increased rapidly above 700 °C. The RMS roughness increased above 800 °C and 700 °C respectively for InAIN and InGaN samples. In droplets began to form on the surface at 900 °C for InAIN and at 800 °C for InGaN, and then evaporate at 1000 °C leaving pits. AES analysis showed a decrease in the N concentration in the top 500 Å of the sample for annealing ≥800 °C in both materials.
Low Volume Resistivity Chemical Vapor Deposited Boron Doped Polycrystalline Thin Diamond Film Growth on Sapphire
Authors: Golestanian Hassan , Mirzakuchaki S. , Charlson E. J. , Stacy T. , Charlson E. M. 
Published: April 2011

AbstractHot-filament chemical vapor deposited (HFCVD) boron doped polycrystalline diamond thin films having low volume resistivity were grown on sapphire. The films were characterized using scanning electron microscope (SEM), X-ray diffraction, and current-voltage measurements. SEM micrographs show good crystalline structure with preferred (100) orientation normal to the surface of the film. X-ray diffraction pattern revealed diamond characteristics with the four typical diamond peaks present. Finally, the obtained I-V characteristics indicated that the film's volume resistivity is at least two orders of magnitude lower than those of HFCVD polycrystalline diamond thin films grown on silicon under similar growth conditions.
Factors Influencing the Electrical and Optical Properties of Aigan Layers on Sapphire
Authors: Shin M. , Polyakov A. Y. , Skowronski M. , Greve D. W. , Wilson R. G. , Freitas J. A. 
Published: April 2011

AbstractEpitaxial layers of A1xGa1-xN were grown by MOCVD on sapphire substrates and characterized by temperature dependent Hall effect, optical absorption, SIMS and photoluminescence. The concentration of native donors was found to decrease with increase of growth temperature. Deep levels found in A1GaN layers were interpreted as A1 double donor state and T2 donor state of nitrogen vacancy.
Influence of Forced Diffusion of Boron on Electrical Conductivity of Diamond Films
Authors: Sung T. , Popovici G. , Prelas M. A. , Wilson R. G. , Bigelow Kim , Chacon J. , Loyalka S. K. 
Published: April 2011

AbstractFour CVD diamond films grown on tungsten carbide were used for diffusion. Diffusion was performed in a hydrogen atmosphere. Three methods of diffusion were used: conventional diffusion due to concentration gradient, forced diffusion under a dc electric bias with thermal ionization and forced diffusion with optical and thermal ionization of boron acceptor level in diamond. The temperature dependence of the electrical conductivity of the diffused samples was measured in the temperature range 300–600 K. The increase of approximately six order of magnitude in conductivity of the films doped by forced diffusion was obtained. The samples diffused with boron by conventional diffusion due to concentration gradient showed only one order of magnitude increase in electrical conductivity.
Measurement of The Activation Energy in Phosphorous Doped Polycrystalline Diamond Thin Films Grown on Silicon Substrates by Hot Filament Chemical Vapor Deposition
Authors: Mirzakuchaki S. , Golestanian H. , Charlson E. J. , Stacy T. 
Published: April 2011

AbstractAlthough many researchers have studied boron-doped diamond thin films in the past several years, there have been few reports on the effects of doping CVD-grown diamond films with phosphorous. For this work, polycrystalline diamond thin films were grown by hot filament chemical vapor deposition (HFCVD) on p-type silicon substrates. Phosphorous was introduced into the reaction chamber as an in situ dopant during the growth. The quality and orientation of the diamond thin films were monitored by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Current-voltage (I-V) data as a function of temperature for golddiamond film-silicon-aluminum structures were measured. The activation energy of the phosphorous dopants was calculated to be approximately 0.29 eV.
Electronic Structure and Temperature Dependence of Excitons in GaN
Authors: Buyanova I. A. , Bergman J. P. , Lil W. , Monemar B. , Amano H. , Akasaki I. 
Published: April 2011

AbstractWe present an optical study of the excitonic properties of epitaxial GaN using reflectivity and photoluminescence (PL) measurements. The values for the intrinsic exciton energies are found to be dependent on the built in strain developed due to the difference in thermal expansion coefficients between the GaN epilayer and the foreign substrate. For GaN on sapphire thecompressive biaxial strain causes an upshift of A and B excitons by typically 15 meV relative to the strain free sample, in accordance with previous data. For GaN on SiC, on the other hand, a downshift ˜ 8 meV in the free exciton energies is observed at 2K. Only two excitonic peaks about 18 meV apart, are resolved in reflectivity spectra for GaN on SiC, probably due to the overlapping of A and B excitons. The suggested explanation implies the reduction of the bandgap energy and of the valence band splitting under the action of a biaxial tensional strain in the GaN layer. For all structures the strain-induced shifts of the bandgap energy are much smaller at elevated temperatures, presumably reflecting the temperature dependence of the accumulated strain energy. The exciton-polariton structure of the GaN is also discussed. The enhanced intensity of the no-phonon (NP) A line compared to its longitudinal (LO) phonon replica is suggested to be partially attributed to strong defect scattering.