bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recovery Kinetics of Phosphorus Ion-Implanted a-Si:H
Authors: Nakata J. , Wagner S. , Gleskova H. , Stolk P. A. , Poate J. M. 
Published: April 2011

AbstractHydrogenated amorphous silicon was implanted with phosphorus ions to a uniform concentration of 3×1020 cm-3 and defect saturation. The implants were annealed isochronally up to 400°C in the dark or under additional illumination. This illumination had no effect on recovery. The Urbach energy remains higher than that of silicon-implants. The midgap defect density anneals to ˜ 1018 cm-3, typical of gas-phase doped samples. The dark conductvity remains lower and its thermal activation energy higher than in gas-phase doped samples. We surmise that the Si-Si network absorbs some of the donor electron-induced defect density by forming strained Si-Si bonds. These strained bonds widen the band tails, and thus reduce the effective electron mobility and pin the Fermi level.
Local Structural Changes Around Charged Dangling Bonds
Authors: Biswas R. , Li Qiming 
Published: April 2011

AbstractTight-binding total energy calculations are used to describe the changes in local structure following either electron or hole capture by a neutral dangling bond in computer generated a-Si:H models. After the change in charge state, the structure is allowed to relax by a steepest descent energy minimization procedure. Generally the local bond angles increase (decrease) rapidly by 3- 100 in transitions from the D0 to the D+ (D-) configurations. The displacement of nearest neighbor atoms and nearby H atoms is large (more than 0.2 Å), but displacement of distant atoms is generally much smaller. Calculated optical transition levels have the D- level below D0 and the D+ level above D0. The fast relaxation of the charged defect configurations suggest a smooth energy surface for the relaxation.
Observation of Configurational Switching of Deep Defects in a-Si:H Using Thermal Step Insertion During Capacitance Transient Measurements
Authors: Gardner Adam D. , Cohen J. David 
Published: April 2011

AbstractIn standard, isothermal capacitance transient measurements, configurational changes in defect states are normally very difficult to identify because, depending on the relative rates of thermal emission to the configurational relaxation, charge will be emitted predominantly from only one configuration. We have found, however, that employing a thermal step during the emission phase of the transient enhances the effect of defect relaxation; one can then observe the resultant switch between distinct configurations. We have applied this method quite successfully to lightly doped n-type a-Si:H samples by varying the overall temperature (between 270K and 350K) and the magnitude of the temperature switch (from 20K to 35K). For the smallest temperature steps, the resultant transients suggest two distinct configurations that, we believe, reflect only a fraction of the many latent configurations that account for the full range of relaxation possible.
CPM and PDS - A Critical Interpretation of Experimental Results
Authors: Stiebig Helmut , Siebke Frank , Carius Reinhard 
Published: April 2011

AbstractCPM and PDS spectra of a-Si:H yield identical shape of the Urbach tail, while the defect absorption measured by PDS differs significantly from CPM. In this work an analysis of CPM and PDS spectra of annealed and degraded films is presented. Numerical simulations of CPM and PDS data, taking into account optical transitions, capture and emission processes as well as the Fermi level, yield information on the energy distribution and the charge state of the defects. The simulations reveal the coexistence of defects in the D−, D+ and D0 states. The defect distribution is dominated by charged states as predicted by the defect-pool model. Good agreement between measured and simulated PDS and CPM spectra can be obtained in the case of a homogeneous defect density. It is shown that differences between CPM and PDS are due to different sensitivities of the techniques to charged and neutral defect states. Microscopic inhomogeneities may cause significant additional differences.
Transient Photoconductivity of a-Si:H at Low Temperatures Induced by Bandgap Light
Authors: Heck S. , Stradins P. , Fritzsche H. 
Published: April 2011

AbstractThe rise and decay of the photoconductivity σp of intrinsic and strongly p-type hydrogenated amorphous silicon (a-Si:H) samples was studied as a function of photocarrier generation rate G between 4.2K and 300K. In intrinsic samples the temperature regime T<60K of energy-loss hopping is clearly distinguishable from T>80K where thermal re-excitation of photocarriers is possible. For the p-type sample the temperature dividing the two regimes is near 170K. In intrinsic samples the rise of σp is faster when residual photocarriers exist from previous light exposures than when the samples are in the electronic dark equilibrium. This indicates that geminate recombination decreases with increasing photocarrier concentration. In the p-type sample we observe an up to 20 percent overshoot in the rise of σp before σp settles down to its steady state value. This overshoot increases with G. We interpret the overshoot as an interplay of two recombination channels with different time scales.
Amorphous Silicon TFTS and Flat Panel Displays
Authors: Tsukada T. 
Published: April 2011

AbstractThe current status and next-generation technologies for liquid-crystal displays based on amorphous silicon TFTs are described. Panel size, resolution, design rule, and viewing angle are discussed from the standpoint of panel performance, productivity, and product application. The material properties for future TFT/LCDs are specified based on the discussions of design rule.
Modulated Hall-Effect Techniques for the Study of Transport Properties of Microcrystalline Silicon with Different Grain Sizes
Authors: Hapke P. , Backhausen U. , Carius R. , Finger F. , Ray S. 
Published: April 2011

AbstractHighly doped μc-Si:H samples with a wide range of crystalline volume fractions and grain sizes have been investigated by Hall-effect experiments. We present an experimental set-up with a current modulation technique and a 6-pole contact geometry which allows the measurement of the Hall-effect on highly doped μc-Si:H down to 10K. The experimental results exhibit a clear correlation between the mobility μ and the grain size δ. Further, the results show that the transport in μc-Si:H can not be described by thermal emission over grain boundaries alone, additional transport paths, e.g. tunneling processes through the barriers have to be taken into account.
Measured and Simulated Temperature Dependence of A-Si:H Solar Cell Parameters
Authors: Stiebig H. , Eickhoff Th. , Zimmer J. , Beneking C. , Wagner H. 
Published: April 2011

AbstractIn contrast to the successful application of analytic equations to the current-voltage behaviour of crystalline silicon solar cells in the dark and under AM 1.5 illumination, the description of a-Si:H solar cells parameters requires device modelling concepts taking the full set of semiconductor equations into account. This in particular holds for the explanation of the temperature dependence (225-400K) of experimentally determined a-Si:H p-i-n solar cell parameters. Device modelling calculations show that the observed decrease of the short circuit current at AM 1.5 with lower T is much more effected by the additional charge trapped in the tail states and recharging of defect states than by the broadening of the gap. The induced electric field distortion blocks the extraction of photo generated holes. The open circuit voltage Voc increases with lower T which is caused by the same trapping effect.
Lead Sulphide Quantum-Sized Particles With Absorption Band Onset in the Near Infra Red
Authors: Bhat J.C. , Krishnakumar T. , Nayak R.R. , Salata O.V. , Hutchison J.L. , Dobson P.J. 
Published: April 2011

AbstractLead sulphide nanoparticles were prepared by colloidal techniques and subsequently deposited onto glass slides as uniform, dry films. In so doing, the effective bandgap of the semiconductor was increased from that of the bulk material by the quantum size effect. By varying the growth conditions, it was possible to change the mean particle size from 3nm to 7nm. This size variation was accompanied by (i) a variation in the absorption band onset of the material from 0.7μm to 1.3μm and (ii) a change in its colour from red to greyish-brown. No excitonic features were observed. TEM showed that the shape of the particles, as well as their size, was dependent on the growth conditions. Cubic and rod-like particles were grown in aqueous solution. Spherical particles preferable for optoelectronic devices were grown in methanolic/aqueous and aqueous solutions. However, these spherical particles were not as reproducible as the cubic ones.
Strain Effects on Optical Gain Properties of GaN/AlGaN Quantum Well Lasers
Authors: Suzuki M. , Uenoyama T. 
Published: April 2011

AbstractSubband structures and optical gains of the strained wurtzite GaN/AlGaN quantum well lasers are theoretically investigated on the basis of k.p theory. First-principles calculations are used for deriving the unknown physical parameters, such as deformation potentials. Neither compressive nor tensile biaxial strains are so effective on the reduction of the threshold carrier density. It is also found that the uniaxial strain in the c-plane is one of the preferable approaches for the efficient improvement of the laser performance.
Comparison of N- And P-Type Ingaas/Inp Quantum Well Infrared Photodetectors
Authors: Sengupta D.K. , Malin J.I. , Jackson S.L. , Fang W. , Wu W. , Kuo H.C. , Rowe C. , Chuang S.L. , Hsieh K.C. , Tucker J.R. , Lyding J. W. , Feng M. , Stillman G.E. , Liu H.C. 
Published: April 2011

AbstractOver an order of magnitude reduction in dark current was observed for gas-source molecular beam epitaxially (GSMBE) grown, lattice-matched n- and p-type InGaAs/InP quantum-well infrared photodetectors (QWIPs). Peak spectral response at 8.93 and 4.55 μm for n- and p-type QWIPs, respectively, open the possibility of dual-band monolithic integration under identical GSMBE growth conditions.
Ecr Etching of GaP, GaAs, InP, and InGaAs in Cl2/Ar, Cl2/N2, BCl3/Ar, and BCl3/N2
Authors: Shul R. J. , Baca A. G. , Rieger D. J. , Hou H. , Pearton S. J. , Ren F. 
Published: April 2011

AbstractElectron cyclotron resonance (ECR) etching of GaP, GaAs, InP, and InGaAs are reported as a function of percent chlorine-containing gas for Cl2/Ar, Cl2/N2, BCl3/Ar, and BCl3/N2 plasma chemistries. GaAs and GaP etch rates were faster than InP and InGaAs, independent of plasma chemistry due to the low volatility of the InClx, etch products. GaAs and GaP etch rates increased as %Cl2 was increased for Cl2/Ar and Cl2/N2 plasmas. The GaAs and GaP etch rates were much slower in BCl3-based plasmas due to lower concentrations of reactive Cl, however enhanced etch rates were observed in BCl3/N2 at 75% BCl3. Smooth etched surfaces were obtained over a wide range of plasma chemistries.
Oxygen-Related Defects in High Purity Movpe Aigaas
Authors: Ryan J.M. , Kuech T.F. , Bray K.L. 
Published: April 2011

AbstractThe near-infrared photoluminescence of high purity, nominally undoped MOVPE AlGaAs was investigated as a function of growth temperature, aluminum content and hydrostatic pressure. Two PL bands, observed at ˜1.1 eV and ˜0.8 eV independent of aluminum content, were attributed to oxygen-related defects based on the correlation of emission intensity and oxygen concentration. Hydrostatic pressure experiments, along with the measurement temperature dependence, suggest that the ˜0.8 eV band is due to emission from an oxygen-related mid-gap level to a shallow acceptor or the valence band, depending on temperature. A tentative defect model based on the off-center OA, defect in bulk GaAs and variations in the number of nearest neighbor aluminum atoms is proposed to explain the two PL bands and the dependence of their relative intensity on aluminum content.
Growth and Characterization of GaAs Epitaxial Layers by MOCVD
Authors: Hudait Mantu Kumar , Modak Prasanta , Krupanidhi S.B. 
Published: April 2011

Abstracttechnique, on both semi-insulating and semi-conducting CraAs substrates with (100) orientation, offset by 2° towards (110) direction. Systematic variation of As/Ga was performed to gain an understanding of growth process, type of formation and other related physical properties. The films were characterized by using the variety of techniques, such as SEM, EDAX, HRTEM, XRD, and PL. Optical and electrical properties of undoped CyaAs epilayers are presented with reference to the growth conditions and AsH3/TMGa ratio. Photoluminescence measurements of GaAs epilayers were recorded at 4.2K and shows the emission of free exciton and confirmed their high purity. The dominant residual impurities in GaAs are presented by using PL. Finally, electrochemical depth profiling exhibited almost homogeneous background carrier distribution and excellent abruptness between the thin GaAs epilayer and substrate.
Atomic Force Microscope Chemically Induced Direct Processing
Authors: Shimbo B. N. , Komarov S. , Vartanian B. J. , Okada Y. , Harris J. S. 
Published: April 2011

AbstractInterest in room-temperature operable quantum effect devices has created a need for simple and inexpensive nanofabrication techniques. By applying a bias to a conductive AFM tip, we have succeeded in fabricating narrow (˜30 nm) oxide lines on a variety of metal and III-V semiconductor substrates. The effects of different drawing parameters such as tip bias, translation speed, ambient atmosphere, and substrate doping on line quality were explored.
Analysis of Radiative Recombination and Optical Gain in Gallium Nitride-Based Heterostructures
Authors: Eliseev Petr G. , Smagley Vladimir A. , Osiński Marek 
Published: April 2011

AbstractThreshold current density in GaN-based UV double-heterostructure lasers is predicted in the range of 2- 4 kA/cm2 using theoretical calculation of optimized heterostructure for various types of devices. Freecarrier (FC) and Coulomb-enhancement (CE) models are compared. Results are given for different combinations of effective masses. The minimum threshold current is not strongly influenced by the choice of effective masses. The FC model predicts lower than CE threshold in edge-emitting lasers, whereas the CE model predicts lower than EC threshold in thin VCSEL devices.
Selective Oxidation of Buried Aigaas for Fabrication of Vertical-Cavity Lasers
Authors: Choquette Kent D. , Geib K. M. , Chui H. C. , Hou H. Q. , Hull Robert 
Published: April 2011

AbstractWe discuss the selective conversion of buried layers of AlGaAs to a stable oxide and the implementation of this oxide into high performance vertical-cavity surface emitting lasers (VCSELs). The rate of lateral oxidation is shown to be linear with an Arrhenius temperature dependence. The measured activation energies vary with Al composition, providing a high degree of oxidation selectivity between AIGaAs alloys. Thus buried oxide layers can be selectively fabricated within the VCSEL through small compositional variations in the AlGaAs layers. The oxidation of AlGaAs alloys, as opposed to AlAs, is found to provide robust processing of reliable lasers. The insulating and low refractive index oxide provides enhanced electrical and optical confinement for ultralow threshold currents in oxide-apertured VCSELs.
The Possible Mechanism of Excitation of the f - f Emission from Er-O Clusters in Silicon
Authors: Masterov V. F. , Gerchikov L. G. 
Published: April 2011

AbstractThe Er2O3 quantum dot (cluster) with dimensions about 1.2nm in silicon is discussed as the possible source of the Er related emission in Si:Er,O, excited by photogenerated carriers or in a light-emitting diodes (LED) at forward bias. This quantum dot is represented as a spherical quantum well 0.9eV in depth. The electron level with energy about 0.15eV below the bottom of the silicon conduction band plays role of an electron trap. The trapped electron interacts with a hole in valence band of silicon forming “indirect” exciton bonded to quantum well. The energy is transferred to f - shell of erbium by the Auger electron - hole recombination.
Photo- and Electroluminescence Study of Excitation Mechanism of Er Luminescence in a-Si:ff(Er)
Authors: Yassievich I. N. , Gusev O. B. , Bresler M. S. , Fuhs W. , Kuznetsov A. N. , Masterov V. F. , Terukov E. I. , Zakharchenya B. P. 
Published: April 2011

AbstractPhoto- and electroluminescence were studied in erbium-doped amorphous hydrogenated silicon films. A mechanism of excitation of erbium ions by defect-related Auger process is proposed which permits to explain consistently the whole set of our experimental results.
Increased Refractive Indices in Rare Earth Doped InP and In0.53 Ga0.47 as Thin Films
Authors: Stadler B. J. H. , Lorenzo J. P. 
Published: April 2011

AbstractRare earth (Gd, Eu, Er) doped InGaAs and InP layers were grown by liquid phase epitaxy (LPE). The refractive index of these layers was observed to increase with the addition of the rare earth ions. The observed increase could not be explained by changes in host composition as typically calculated from changes in lattice parameter. In fact, the refractive index was seen to increase (∼0.25) by an order of magnitude more than would be expected by the change in the lattice parameter (∼0.02). The increased refractive indices of InP layers due to Er-doping enabled waveguiding. These findings suggest that optically active waveguide devices can be fabricated from semiconducting hosts by simple rare earth doping.
Optical Centers Related to Laser-Doped Erbium in Silicon
Authors: Nakashima K. , Eryu O. , Iioka O. , Minami H , Watanabe M. 
Published: April 2011

AbstractExcimer laser irradiation has been applied to dope erbium ions in silicon. Er-doping is realized with both processes of the Er-diffusion in the melted region and the subsequent solid solidification. Er atoms at the maximum concentration of 1021 cm3 are doped in the region of 150 nm thickness without significant defect formation and amorphization. Stable Er-optical centers, emitting well known series of luminescence lines near 1.54 jim, are formed after short term heat treatments at a relatively low temperature. Optical centers are distributed in proportional to the total Er concentration in the doped region. Oxygen atoms are found to play critical roles for stabilizing Er-optical centers and for rearranging the surroundings of Er ions. Modified bonding states of O and Er other than those in SiO2 or Er2O3 are formed in the Er doped region during both doping and annealing processes.
Silicon Carbide Cvd Approaches Industrial Needs
Authors: Rupp R. , Lanig P. , Völkl J. , Stephani D. 
Published: April 2011

AbstractIn this paper an overview is given on the current state of epitaxial growth of SiC with special regard to our work at SIEMENS CRD. Problems concerning impurity incorporation and ways to achieve background doping levels as low as 1014 cm−3 are discussed as well as the influence of high speed wafer rotation on the gas flow in our reactor and related effects on uniformity in thickness and doping. Precise control of the C/Si ratio in the gas phase, which is easily achieved in the described reactor, and the use of reduced pressure lead to a good control of dopant incorporation over more than 3 orders of magnitude while maintaining smooth surface morphology even at growth rates higher than 5 μm/h. Doping variations <±8 % across 30 mm wafers can routinely be obtained. The quality of the egilayers is proven by electrical breakdown fields as high as 2*106 V/cm at NA−ND=5* 10−15 cm−and an electron mobility greater than 700 cm2 /Vs at 300 K (4H-SiC).Finally it is demonstrated that the gas composition at the end of the epitaxial growth process is an important step in order to get oxygen resistant surface properties for subsequent device processing.
The Impact of Pregrowth Conditions and Substrate Polytype on SiC Epitaxial Layer Morphology
Authors: Burk A. A. , Rowland L. B. , Augustine G. , Hobgood H. M. , Hopkins R. H. 
Published: April 2011

Abstract4H and 6H-SiC epitaxial layers exhibit characteristic morphological defects caused by process and substrate interferences with the a-axis directed step-flow growth. 4H-SiC is shown to typically exhibit worse morphology than 6H-SiC for a given off-axis orientation. SiC epitaxial layer defects are significantly reduced by the optimization of growth conditions and substrate surface preparation. The remaining highly variable defects are shown to emanate from the substrate surface with densities of ≥1000 cm−2
Seeding With a Diamond Suspension for Growth of Smooth Polycrystalline Diamond Surfaces
Authors: Omer I. St. , Stacy T. , Charlson E. M. , Charlson E. J. 
Published: April 2011

AbstractA number of techniques have been used to smooth polycrystalline diamond films. Recent work in substrate seeding with nanocrystalline diamond powder, alone or in a carrier fluid, has shown that diamond seeding improves nucleation density and reduces diamond surface roughness. In this work, silicon substrates were seeded using a commercially available waterbased 0.1 micrometer diamond polishing suspension. Growth was achieved using conventional hot-filament chemical vapor deposition (HFCVD). Films were characterized using optical microscopy, scanning electron microscopy (SEM), x-ray diffraction (XRD), and surface profilometry. The resulting diamond films exhibited well-faceted crystals, small grain size and minimal surface roughness. Additionally, the silicon substrate was chemically etched in order to permit examination of the backside of the diamond film. Results show that the diamond surface at the silicon-diamond interface is ultra-smooth. Comparison of the backside of these surfaces with those prepared using conventional diamond grit abrasion indicates that a significant improvement in surface quality is achieved using this diamond seeding technique.
SiC Semiconductor Applications - An Air Force Perspective
Authors: Rea L. S. 
Published: April 2011

AbstractThe Department of Defense (DoD) is investing in the development of Silicon Carbide (SiC) for a wide range of applications. Over the past year, SiC technology has demonstrated excellent device performance results for power devices, high temperature electronic devices and microwave devices. The materials growth and processing technology for SiC is now at a level of sufficient maturity to support substantial device development efforts. While there is still considerable materials and device research required for SiC to achieve it's full potential, the fundamental technology has been proven for several critical applications. A perspective on some Air Force device performance requirements will be presented. The status of SiC materials development, material limits to advances in device performance and issues relating to supporting technology will also be discussed.
X-Ray Diffraction Analysis Of Strain And Mosaic Structure In (001) Oriented Homoepitaxial Diamond Films
Authors: Alexander W. Brock , Pehrsson Pehr E. , Black David , Butler James E. 
Published: April 2011

AbstractHomoepitaxial diamond films were grown on (001) oriented high pressure, high temperature type lb diamond by microwave plasma-assisted chemical vapor deposition to thicknesses of 27–48 μm. Substrates were polished off-axis 5.5° ±0.5° in the [100] direction prior to film deposition. Some of the diamond films developed tensile stress sufficiently large to result in cracking on { 111 } cleavage planes, while other films exhibited compressive stress. The strain and mosaic structure were measured with seven crystal x-ray diffraction. This characterization tool allowed the separation of misorientation effects from those of lattice parameter variation. Films exhibited smaller (˜88 ppm) and larger (˜27 ppm) perpendicular lattice parameters relative to the HPHT substrates. A cross-sectional approach for probing strain in diamond films with micro-Raman analysis was used to show stress distributions (˜100–300 MPa) through the thickness of the film.