bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transient Mean-Field Reaction-Diffusion Model Applied to Hydrogen Evolution From Hydrogenated Amorphous Silicon
Authors: Franzi A. J. , Mavrikakis M. , Schwank J. W. , Gland J. L. 
Published: April 2011

ABSTRACTHydrogen bulk mobility plays an important role in determining a wide range of materials and electronic properties of hydrogenated amorphous silicon (a-Si:H). The existence of two types of hydrogen traps plays an important role in controlling hydrogen mobility in, and evolution of hydrogen from a-Si:H, however, theoretical and experimental literature values for the trap energetics vary considerably. We have developed a mean-field reaction-diffusion model which explicitly includes two trap states and realistic surface processes to model hydrogen evolution from a-Si:H. Modern numerical techniques were required to solve this challenging problem over the wide range of temperatures and concentrations encountered in typical hydrogen evolution experiments. The model is based on a number of experimentally established parameters. Comparison of our rigorous model with temperature programmed hydrogen evolution experiments provides a powerful method for characterizing the energetics, trap concentrations and diffusivity of hydrogen in a-Si:H.
Is Thermal and Light-Induced Annealing of Met Astable Defects in a-Si:H Driven by Electrons?
Authors: Gleskova Helena , Wagner S. 
Published: April 2011

ABSTRACTWe report results of a search for a unifying rate law for the annealing of metastable defects in hydrogenated amorphous silicon (a-Si:H). We tested the hypothesis that defect-annealing by both heating or illumination is driven by the density of free electrons. This hypothesis is formulated via the rate equation - dN/dt = A nα N f (T), where N is the defect density, t the time, A a constant, n the free electron density, and f (T) a function of temperature derived from a distribution of annealing energies. The model fits two sets of data, with light-intensity and electrical conductivity as the independent variables, reasonably well, with a ranging from 0.39 to 0.76, but not the third set, where we varied the temperature.
Telegraph Noise as A Probe of Microscopic Hydrogen Motion in Amorphous Silicon
Authors: Lust Lisa M. , Kakalios J. 
Published: April 2011

ABSTRACTTime traces of conductance fluctuations in the co-planar current of hydrogenated amorphous silicon (a-Si:H) display sharp jumps between discrete resistance levels, termed random telegraph switching noise (RTSN). Measurements of the temperature dependence and effects of light soaking of the RTSN in n-type doped a-Si:H are reported. The rise times between the two level fluctuators yield activation energies and attempt to hop frequencies for microscopic hydrogen motion which agree with those obtained from NMR experiments. Computer simulations of a dynamical percolation random resistor network support the suggestion that the RTSN arises from local diffusion processes altering the conductance of inhomogeneous current filaments.
Electron Drift Mobility in a-Si:H Prepared by Hot-Wire Deposition
Authors: Gu Qing , Schiff E. A. , Crandall R. S. , Iwaniczko E. , Nelson B. 
Published: April 2011

ABSTRACTWe have measured the electron drift mobility in a-Si:H prepared by hot wire (HW) deposition using photocarrier time-of-flight. Initial work has shown that light-soaked HW material can have much better ambipolar diffusion lengths than the plasma-deposited material following extended light soaking. In a sample with about 2% H-concentration in the intrinsic layer, we find that the electron drift mobility is quite different from that of a-Si:H alloys prepared by normal glow-discharge CVD, even allowing for the reduced bandgap of the hot Wire material. This result challenges the principle that the bandgap of optimized amorphous silicon based material is sufficient to predict the electron drift mobility.
Phototransport Properties of a-SiC:H Alloys
Authors: Nery G. , Ramirez A. , Resto O. , Weisz S. Z. , Lubianiker Y. , Balberg I. 
Published: April 2011

ABSTRACTWe report a study of the mobility-lifetime products of the two charge carriers in a-SiC:H alloys. The measurements were carried out as a function of the carbon concentration and the temperature. An analysis, relying on the interpretation of the corresponding light intensity exponents, indicates that neutral dangling bonds control the electrons' lifetime while another recombination center controls the holes' lifetime.
Time Dependence of Spatial Defect Profiles in a-Si:H Solar Cells with Light-Soaking
Authors: Caputo D. , Maggi M. , Masini G. , Palma F. , Vasanth K. , Wagner S. 
Published: April 2011

ABSTRACTWe report on modeling the evolution of the spatial defect profile in the i-layer of a-Si:H solar cells combined with tests of the model against the efficiency decay of amorphous silicon (a-Si:H) p-i-n solar cells under various light-soaking conditions. We use a finite-element device simulator. The defect density during light-soaking is calculated as a function of time and of position. The defect density evolves due to the combined effects of light-induced generation, assumed proportional to the product of free carrier densities, and of light-induced annealing, assumed proportional to the sum of carrier densities. We find that in thick cells defects close to the p-i interface affect cell efficiency less than bulk defects, and that in thin cells the defect density increases significantly in the central portion of the i-layer. However, in thin cells the high electric field masks the effect of the defect density increase.
Deuterium Incorporation into Glow-Discharge Deposited Deuterated-Hydrogenated Amorphous Silicon
Authors: Sidhu L. S. , Gaspari F. , O'Leary S. K. , Zukotynski S. 
Published: April 2011

ABSTRACTWe investigate deuterium incorporation into deuterated-hydrogenated amorphous silicon grown by the saddle-field glow-discharge of deuterium and silane. The presence of HD and SiH3D in the discharge suggests strong gas phase mixing. The dominant process of deuterium incorporation into the growing film appears to be the direct reaction between deuterium and the growth surface.
Passivation Studies on AlGaAs Surfaces Suitable for High Power Laser Development
Authors: Edirisinghe C. , Ruda H. E. , Koutzarov I. , Liu Q. , Jedral L. , Boudreau M. G. , Boumerzoug M. , Brown J. , Mascher P. , Moore A. , Henderson R. 
Published: April 2011

AbstractWe report on the optical characterization of sulphur (S) passivated AlxGa1−xAs/GaAs surfaces using photoluminescence (PL) and surface photovoltage (SPV) measurements. Both techniques show an enhancement in the near bandgap signal intensity, implying a reduction of the non-radiative recombination rate at the surface. To counter the instability of S-passivation, due to re-oxidation, dielectric layers of silicon nitride were deposited using electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR-PECVD); the deposition of dielectric layers up to lOOnm thick does not appear to cause significant deterioration or stress at the insulator/AlGaAs interface. The dielectric layers are shown to be resistant to oxidation, and effective in maintaining the passivation effect over a period of weeks.
Deep Impurities in AlGaAs Grown by MOCVD Using Different Hydrogen and Nitrogen as Carrier Gases
Authors: Chen J. C. , Huang Z. C. , Yang Bing , Chen H. K. , Lee K. J. 
Published: April 2011

AbstractA study was carried out to characterize the deep impurities in AlxGa1-x As grown by metal-organic chemical vapor deposition (MOCVD) using different carrier gases. Since AlxGai1-x As is very sensitive to any impurities, especially moisture and oxygen, in the growth process, the concentration of impurities in AlxGai1-xAs can serve as a measure of the purity of carrier gases. The undoped AlGaAs layers grown by using H2 have n-type background concentrations from 3×1015 to 10×1015/cc. The concentrations of oxygen-related traps (Ec−0.53 and 0.7 eV) are 0.2−9×1013 and 3.4−5×1014/cc for Pd- and Li-purified H2, respectively. Low-temperature photoluminescence (PL) measurements show better PL efficiency in samples grown by using Pd- purified H2. AlxGa1-xAs grown by using N2 is p-type (p∼6×1016/cc) with an oxygen-related trap and two hole traps. The concentration of oxygen-related trap is more than one order of magnitude higher than that of AlGaAs using Pd-purified H2. The memory effect due to impurities from carrier gas left in source materials is also studied.
Low Deep Impurity InxGa1-xP Grown by Metalorganic Chemical Vapor Deposition
Authors: Huang Z. C. , Yang Bing , Chen H. K. , Chen J. C. 
Published: April 2011

AbstractInxGai-xP (x=0.49) layers lattice-matched to GaAs have been grown by metalorganic chemical vapor deposition (MOCVD). We did not observe any deep levels in the temperature range of 30-380K by deep level transient spectroscopy (DLTS) in undoped In0.49Ga0.51P layers which have a background concentration of 3.1×1015 cm−3. The deep levels, if they exist, have a concentration of less than 5×1011 cm−3, which is the lowest deep level concentration found so far in InxGa1-xP materials. Moreover, lattice-mismatched InxGa1-xP/GaAs heterojunctions were deliberately grown by varying the In-composition ranging from 0.43 to 0.57. No deep levels were created in 1-μm-thick InxGa1-xP layers due to lattice mismatch when 0.469 < x < 0.532. However, we have observed a shallow electron trap at EC - 60 meV in InxGa1-xP layers with x < 469, and a deep electron trap located at Ec - 0.85 eV in the samples with x > 0.532. We suggest that the lattice-mismatch-induced-defects in InxGa1-xP are either electrically inactive or resided outside the bandgap when In content ranging from 0.469 to 0.532.
Optical Absorptions and EL2-Like Defects in Low Temperature Grown Molecular-Beam-Epitaxial GaAs
Authors: So S. K. , Chan M. H. , Chan K. T. 
Published: April 2011

Abstract:The optical absorptions and the defect densities of GaAs grown by low temperature molecular-beam-epitaxy at growth temperatures between 200-580 °C were evaluated by photothermal deflection spectroscopy. The shapes of the absorption spectra exhibit EL2-like characteristics. Defect densities were found to be in the range of 1018-1019 cm−3. The PDS phase spectra were shown to be useful to differentiate the absorptions of the epilayer from those of the bulk.
On the Recombination Activity of Oxygen Precipitation Related Lattice Defects in Silicon
Authors: Vanhellemont J. , Kaniava A. , Libezny M. , Simoen E. , Kissinger G. , Gaubas E. , Claeys C. , Clauws P. 
Published: April 2011

AbstractThe recombination activity of oxygen precipitation related lattice defects in p- and n-type silicon is studied with photoluminescence (PL) and microwave absorption (MWA) techniques. A direct correlation is observed between the amount of precipitated oxygen and the extended defect density on one hand and the minority carrier lifetime and PL activity on the other hand. The PL analyses show as dominant features in the spectra the Dl and D2 lines. The relative amplitude of the D-lines in the different samples is investigated as a function of the oxygen content, defect density and excitation level. The results are correlated with those of complementary techniques and are interrelated on the basis of Shockley-Read-Hall (SRH) theory.
ECR Hydrogen Plasma Treatment of Si: Defect Activation Under Thermal Anneal
Authors: Nam C. W. , Ashok S. 
Published: April 2011

AbstractSi wafers subject to short-time (4–12 min.), low-temperature atomic hydrogen cleaning in an electron cyclotron resonance (ESR) plasma system have been annealed subsequently in the temperature range 300–750 °C for 20 mins. While only a small broad peak is seen immediately after hydrogenation, several pronounced and distinct majority carrier trap levels show up in deep level transient spectroscopy (DLTS) measurements of subsequently fabricated Schottky diodes on samples annealed at 450 °C and above. The concentrations of these deep levels reach a maximum at anneal temperatures around 500 °C and drop substantially beyond 750 °C. This phenomenon appears to be unrelated to the presence of oxygen in Si and is of potential importance in silicon processing technology.
Hydrogen and Lithium Passivation of Gold in Silicon: A Comparative Study
Authors: Sveinbjörnsson E. ö. , Kristjansson S. , Engström O. , Gislason H. P. 
Published: April 2011

AbstractWe report studies of passivation of the gold center in silicon by hydrogen and lithium using deep level transient spectroscopy (DLTS), capacitance voltage (CV) profiling and secondary ion mass spectroscopy (SIMS). Both lithium and hydrogen are able to remove the electrical activity of the gold center from the silicon band gap but the passivation mechanisms are different. In the case of lithium the passivation is most likely due to a Coulomb attraction between lithium donors Li+ and gold acceptors Au−. No complex formation is observed between Li+ and Au0. In contrast, hydrogen is able to passivate the gold center without the need of opposite charge states of the species involved. Two Au-H complexes are observed, one (G) electrically active, and another (PA) passive. Based on the annealing kinetics of these complexes we propose that the active complex is a Au-H pair and that the passive complex contains two H atoms (Au-H2).
Hydrogen-Induced Passivation of Deep Traps in n-GaAs:Si Grown on LT-GaAs
Authors: Paloura E. C. , Ginoudi A. , Theys B. , Chevallier J. , Lioutas C. B. , Kalomiros J. , Lagadas M. , Hatzopoulos Z. 
Published: April 2011

AbstractWe study the hydrogen-induced passivation of interface traps in n-GaAs:Si, grown by MBE at 580°C, with a buffer layer grown at 200 to 250°C (LT-buffer). In the as-grown samples, the LT-buffer contains As-precipitates, with a density of 4×1016 cm−3 and a diameter that depends on the LT-buffer growth temperature and takes values in the range 4–8nm. The epilayer/LT-buffer interface in the as-grown samples is characterised by interface related traps which dominate the electrical behaviour of the epitaxial layer. Secondary ion mass spectroscopy profiling of deuterated samples reveals that 2H has a nearly uniform concentration throughout the epilayer, while it accumulates at the interface. Hydrogenation induces a reduction of the interface trap concentration and a significant improvement of the carrier mobility values.
High Resistivity InAIN by Nitrogen or Oxygen Implantation
Authors: Zolper J. C. , Pearton S. J. , Abernathy C. R. , Vartuli C. B. 
Published: April 2011

AbstractWe report on the isolation properties of In0.75Al0.25N implanted with either N or O for several doses and post-implant anneal temperatures. Sheet resistance versus anneal temperature data are reported for the various implants with a maximum sheet resistance of <1×109 Ω/□ achieved for a high dose N-implant annealed at 600 or 700 °C and <5×108 Ω/□ achieved for a high dose O-implant annealed at 600 °C. These sheet resistances correspond to a greater than three order of magnitude increase over the as-grown values. The compensating defect level for the highest resistance N-implanted sample has an estimate ionization level 580 meV below the conduction band edge. Implant isolation of InAIN is also compared to oxygen implant isolation of InxGa1-xN — where only a 50 to 100 fold increase in sheet resistance is observed — to study the effect of Al in the isolation scheme.
Silicon Delta Doping in GaAs: An Ongoing Enigma
Authors: Newman R. C. , Ashwin M. J. , Wagner J. , Fahy M. R. , Hart L. , Holmes S. N. , Roberts C. 
Published: April 2011

AbstractInfrared (IR) absorption and Raman scattering are reported from the localized vibrational modes (LVM) of Al and Si δ-layer superlattices in MBE (100) GaAs grown at 400°C as a function of the total areal concentrations, [A1]A and [Si]A respectively. The Al superlattices show the expected behavior on passing from sub-monolayer (ML) to thicker layers (thin AlAs) since the impurities still occupy only Ga-sites. The behavior is very different from that found for Si δ-layers. In addition to SiGa reported previously, we now show that SiAs, SiGa-SiAs pairs and the electron trap Si-X are also present in Si δ-layers and superlattices for 0.05 ≤ [Si]A≤ 0.5 ML. The conductivity of these structures and the concentrations of substitutional Si in GaAs at all sites fall to zero for [Si]A> 0.5 ML but a Raman feature at 470–490 cm−1, attributed to the vibrations of covalent Si-Si bonds is then detected. This feature is not observed in structures containing very closely spaced dilute (0.01 ML) Si δ-planes. It is inferred that long-range Si diffusion does not occur in the bulk crystal, although there could be surface diffusion during Si deposition. The maximum measured carrier concentrations are always less than 2 × 1019 cm−3, the DX limit. The redistribution of Si amongst the various lattice sites is discussed in terms of SiGa DX-like displacements occurring during growth, followed by local thermally activated diffusion jumps. It is speculated that AsGa antisite defects and Ga-vacancies are produced by this process. The reason why the Si δ-layer is non-conducting remains unclear.
Activation of Implanted Phosphorus Ions into Silicon by Followed Hydrogen Ion Implantations
Authors: Hasebe Y. , Ohshima H. , Hattori T. , Usami A. , Tokuda Y. 
Published: April 2011

AbstractThe activation of phosphorus implanted into n-type silicon (100) substrate by followed hydrogen ion(H +) implantation was studied by means of spreading resistance technique(SR), secondary ion mass spectroscopy(SIMS) and transmission electron microscopy(TEM).“The activation ratio” defined by carrier concentration divided by phosphorus concentration was used as a measure of activation of phosphorus. The H + energy, dose and dose rate dependence of activation ratio of phosphorus was investigated.In the case of thermal annealing at 400 °C for 200 minutes the phosphorus atoms were not activated, on the other hand in the case of H + implantation at 400 °C the phosphorus atoms were activated and the activation ratio was increased almost proportionally with the dose. The SIMS data suggested that the depth profile of phosphorus atoms was not changed after activation by H + implantation. The activation ratio was increased with decreasing the dose rate. The TEM data suggested that the density of residual defects was reduced in the case of lower dose rate. The depth profile of activation ratio was similar to that of hydrogen atoms implanted at 20 °C. From these results the activation and recrystalization mechanism is discussed in the view of contribution of elastic collision process between H + ions and substrate atoms.
A Model for the Frequency Dependence of Charge Pumping Current in Polycrystalline Silicon Thin Film Transistor
Authors: Lee Ga-Won , Lee Jung-Yeal , Choi Deuk-Sung , Hur Sung-Hoi , Kim Choong-Ki , Han Chul-Hi 
Published: April 2011

AbstractMaking a comparative study between MOSFET and polycrystalline silicon thin film transistor(poly-Si TFT) in applying the charge pumping method(CPM), the most distinctive difference was found in the relation of the charge pumping current(Icp) versus the gate pulse frequency. According to the conventional theory, Icp increases linearly with the gate pulse frequency. In poly-Si TFT, however, Icp shows complicated dependence on frequency. We modeled the frequency dependence of Icp in poly-Si TFT by considering the resistance of active poly-Si film. According to this model we can extract the parameters such as grain boundary trap density, substrate resistance, and capture cross section.
Investigation of Resistivity Distributions in CdTe Crystals by Time Dependent Charge Measurements (TDCM)
Authors: Eiche C. , Joerger W. , Fiederle M. , Schwarz R. , Salk M. , Ebling D. G. , Benz K. W. 
Published: April 2011

AbstractSpatially resolved resistivity measurements of CdTe crystals doped with Titanium (Ti) and Vanadium (V) were performed. From the temperature dependence of the resistivity the spatial variation of the thermal activation energy was deduced. Variations in axial as well as radial direction were observed and qualitatively explained by a combined segregation and compensation model. It is based on the deep donor levels of Ti and V at 0.95 eV below the conduction band.
Temperature Dependence of Metal-Semiconductor Contacts on 6H-SiC.
Authors: Smith S.R. , Evwaraye A.O. , Mitchel W.C. 
Published: April 2011

AbstractWe have examined the temperature dependence of the barrier height of Au, Ag, Ni, and Al, metal-semiconductor contacts on n-type 6H-SiC, and Al metal-semiconductor contacts on p-type 6H-SiC. The barrier height was determined from the (1/C2) vs VRcharacteristics of the contacts at temperatures ranging from 300K to 670K. The measurements were made at 1 MHz. These measurements were compared to I-V measurements at various temperatures, and to the behavior predicted by standard models.
Classical and Rapid Thermal Process Effects on Oxygen and Carbon Precipitation in Silicon
Authors: Mahfoud K. , Loghmarti M. , Muller J. C. , Siffert P. 
Published: April 2011

AbstractWe report observations on the effects of rapid thermal annealing on oxygen and carbon content of different single and multicrystalline silicon materials.From the comparison between the resulting effects of conventional and short thermal annealing, we can deduce that the increase of the concentration of interstitial oxygen after a rapid thermal annealing (RTA) is due to the dissociation of some microprecipitates in silicon, which is significantly affected by the initial oxygen content, thermal history, defects and impurity content such as carbon.
Large In-Plane Lattice Expansion in NiAs-MnSb Thin Films Induced by ns Laser Recrystallization
Authors: Kubota Yukiko , Gorman Grace L. , Marinero Ernesto E. 
Published: April 2011

ABSTRACTSputter deposited MnSb thin films were annealed utilizing KrF excimer laser pulses (16ns), and the resulting structural and magnetic changes investigated. These changes are compared to those observed when the samples are subjected to isothermal and rapid thermal annealing treatments. Isothermal and rapid thermal annealing induce significant lateral grain growth, whereas the laser treatment produces vertical grain size refinement with no appreciable lateral growth. Annealing is shown to increase the hexagonal c-axis, reaching an expansion value of 7% for the laser annealed samples. This c-axis expansion has a strong influence on the magnetic properties of the thin films. Mechanisms for the c-axis expansion are discussed.
Time Dependent Magnetic Switching in Spin Valve Structures
Authors: Restorff J. B. , Wun-Fogle M. , Cheng S. F. , Hathaway K. B. 
Published: April 2011

ABSTRACTWe have observed time dependent magnetic switching in spin-valve sandwich structures of Cu/Co/Cu/Fe films grown on silicon and Kapton substrates and Permalloy/Co/Cu/Co films grown on NiO or NiO/CoO coated Si substrates. The giant magnetoresistance (MR) values ranged from 1 to 3 percent at room temperature. The films were grown by DC magnetron sputter deposition. Measurements were made on the time required for the MR to stabilize to about 1 part in 104 after the applied field was incremented. This time depends almost linearly on the amplitude of the timedependent MR change with a slope (time / ΔMR) of 20 000 to 30 000 s. Some samples took as long as 70 s to stabilize. The time dependent effects may be important for devices operating in these regions of the magnetoresistance curve. In addition, measurements were made on the time history of the MR value for a period of 75 s following a step change in the field from saturation. We observed that the time dependent behavior of the MR values of both experiments produced an excellent fit to a function of the form ΔMR(t) = α + β;ln(t) where ɑ and β are constants. This time dependence was consistent with the behavior of the magnetic aftereffect.