bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of Growth and Recovery of Light-Induced Defects Under High-Intensity Illumination
Authors: Isomura Masao , Wagner Sigurd 
Published: March 2011

ABSTRACTWe report a study of the rates of generation and of annealing of the light-induced defects in hydrogenated amorphous silicon (a-Si:H). The rates of generation are found to be sensitive to temperature when the light intensity is high. This increased sensitivity to temperature at high rates suggests that a temperature-activated process such as hydrogen motion controls the rates of generation more when they are high. The rate of annealing at 130°C is strongly accelerated by illumination, and depends strongly on the light intensity. This may be explained by the diffusion of hydrogen, accelerated by excess carriers.
Toward the Elimination of Light-Induced Degradation of Amorphous Si by Fluorine Incorporation
Authors: Deng X. , Mytilineou E. , Young R. T. , Ovshinsky S. R. 
Published: March 2011

ABSTRACTWe report on evidence that fluorine, properly incorporated into a-Si, replaces weakly bonded hydrogen and improves the material stability under light soaking. Our fluorinated amorphous silicon (a-Si:H:F) is made by if glow discharge at high deposition temperatures up to 430 C from a gas mixture of SiH4 or Si2H6 and F2. These a-Si:H:F films show much lower density of states in the light soaking saturated state than device quality a-Si:H prepared in the same deposition system. It is evident from our results that fluorine incorporated into the network at such high deposition temperature makes for a new configuration which minimizes dangling bonds and other defects.
The Vibrational Spectrum of a-SiC:H Films in the 500 cm-1 to 9000 cm-1 Range by Ftir Transmission and Photothermal Deflection Spectroscopy
Authors: Lotter E. , Bauer G.H. 
Published: March 2011

ABSTRACTApplying PDS in the energy range from 3000 to 9000 cm-1 considerably improves the sensitivity of vibrational spectroscopy of thin films. In a-SiC:H we have found a large number of absorption features not seen before, which give new insight in structural and compositional properties of these alloys.In a-SiC:H, in addition to the fundamental and the first and second overtone of C-H stretching modes, O-H vibrations occur at 3500 cm-1 and allow a very sensitive detection of chemical degradation of films due to in-diffusion of water. Combined excitation of C-H stretching and C-H wagging or bending modes give rise to a modified interpretation of the origin of the C-H related absorption features observed in methane based a-SiC:H. The induced absorption of molecular hydrogen together with a band at 7000 cm-1, which results from a combined excitation of C-H bonds and H2 molecules colliding with the C-H, indicates that the amount of H2 increases with C alloying. The C-H + H2 combination mode is very strong compared to the corresponding Si-H + H2 peak observed in pure a-Si:H and signalizes mat a considerable amount of the molecular hydrogen enclosed in voids, containing CH3 or CH2 groups.
Anomalous Carbon Interdiffusion in a-Si:H/a-SiC:H Multilayers
Authors: Schwarz R. , Fischer T. , Hanesch P. , Lanz J. , Schirmacher W. , Kolodzey J. , Zorn G. , Goebel H. 
Published: March 2011

ABSTRACTThe interdiffusion of carbon in a-Si:H and a-Si1-xCx:H multilayers is measured by analyzing the time evolution of the X-ray diffraction from the superlattices. A time dependent diffusivity D(t)which follows a power law is found. The theoretical analysis shows that such a time dependence, referred to as “dispersive” or “anomalous” diffusion and studied for hydrogen diffusion in the literature, is fundamentally related to the amorphous structure of the material.
Optoelectronic Properties of Plasma CVD a-Si:H Modified by Filament-Generated Atomic H
Authors: Li Y.M. , An I. , Gunes M. , Dawson R.M. , Collins R.W. , Wronski C.R. 
Published: March 2011

ABSTRACTWe have studied a-Si:H prepared by alternating plasma deposition with atomic H treatments performed with a heated W filament. Real time spectroscopie ellipsometry provides the evolution of film thickness, optical gap, and a measure of the fraction of Si-Si bonds broken in the near-surface (200 Å) during H-exposure of single films. This information guided us to the desired parameters for the H-treatments. Here, we concentrate on a weak hydrogenation regime characterized by minimal etching, a higher H content by 2 at.%, and a larger optical gap by 0.02 eV for the growth/hydrogenation structures in comparison to continuously deposited control samples. This new material has shown an improvement in the defect density in the light-soaked state in comparison to the control samples. This may result from stabilization of the Si structure due to an increase in the H chemical potential in the a-Si:H.
A New Method of Depositing Amorphous Hydrogenated Silicon Carbide with Low Ir-Detected Microstructure
Authors: Lu Hsueh Yi , Petrich Mark A. 
Published: March 2011

ABSTRACTWe report a new method of depositing amorphous hydrogenated silicon carbide thin films with low IR-detected microstructure in a plasma-enhanced chemical vapor deposition reactor. Films prepared at various conditions are studied with Fourier-transform infrared absorption. Their optical band gaps and photoconductivities are also measured. The amount of microstructure can be controlled by adjusting the powered-electrode potential during deposition, and the microstructural changes are reflected in the film properties. By applying an external dc voltage to the rf-excited powered electrode, we can shift the optimal deposition temperature from 250 °C to as low as 100 °C. We find that films deposited at positive powered-electrode potential and low substrate temperature exhibit less microstructure, wider optical band gaps, and faster deposition rates than films deposited at conventional conditions.
Review of the Simulation of Transient Experiments on Amorphous Silicon Hydride
Authors: Shapiro Finley R. 
Published: March 2011

ABSTRACTThe transient characteristics of amorphous silicon hydride (a-Si:H) devices are of great importance as a means of studying the fundamental electrical and photo-electrical processes in the material. To assist in the interpretation of these experiments, several groups have performed simulations to understand better the meaning of transient waveforms. Simulations begin with hypotheses of how the processes of interest affect each other and affect the measured quantity, and then calculate an expected experimental result. Transient experiments on a-Si:H have been simulated by a variety of techniques, including the Monte Carlo, Laplace transform, and time integration methods. Of these methods, time integration is the most powerful but also the most demanding on computer capabilities. Fortunately, recent advances in computer technology have brought the simulation of transient experiments on a-Si:H by time integration within the capabilities of advanced personal computers.
The Spectral Dependence of the Non-Radiative Efficiency in Hydrogenated Amorphous Silicon
Authors: Fan J. , Kakalios J. 
Published: March 2011

ABSTRACTThe room temperature non-radiative efficiency, defined as the ratio of the heat released per absorbed photon for doped and undoped hydrogenated amorphous silicon (a-Si:H) has been measured using photo-pyroelectric spectroscopy (PPES) for photon energies ranging from 2.5 to 1.6 eV. There is a fairly sharp minimum in the non-radiative efficiency when the a-Si:H is illuminated with near bandgap photons. We describe a model wherein this minimum arises from the variation in the amount of heat generated by free carrier thermalization as the incident photon energy is varied, and report measurements of the excitation kinetics of the non-radiative efficiency which support this proposal.
An Assessment of the Light Modulated Photocurrent Method in the Study of the Density of Gap States in Hydrogenated Amorphous Silicon
Authors: Zhong Fan , David Cohen J. 
Published: March 2011

ABSTRACTWe have applied the modulated photocurrent (MPC) method over a wide range of frequencies (5Hz-100kHz) and temperatures (120K-380K) to assess its ability to accurately deduce the mobility gap distribution in a-Si:H. We have also investigated the effects of moving both the Fermi level within some samples (by light soaking and partial annealing) and the quasi-Fermi level (by applying the bias light) to observe how such changes influence the deduced density of states (DOS). We then compared the MPC results directly with the DOS determined by junction capacitance measurements in the same sample devices. We have determined general conditions under which, we believe, the MPC results provide an accurate picture of the gap state distribution. However, we found that under other conditions, the appearance of the deep defect peaks and other features do not represent the actual defect distribution but, rather, are artifacts due to recombination processes.
Electron and Hole Transport in a-SiH at High Field and Low Temperature
Authors: Nebel C. E. , Street R. A. 
Published: March 2011

ABSTRACTLow temperature, high field properties of electron and hole transport are investigated by time-of-flight (TOF), steady-state and transient space charge limited current (SCLC) experiments on intrinsic a-Si:H. Charge collection and TOF experiments performed at T= 80 K reveal hole μτ-products of = 8 × 10-10 cm2/V and hole mobilities μ ≤ 9×10-3 cm2/Vs. The field effect on hole thermalization is demonstrated by evaluation of the post transit current decay. SCLC experiments on p+ -i-n+ (electron transport) and p + -i-n+ (hole transport) configurations are introduced and interpreted in terms of field enhanced conductivity and mobility. The experiments demonstrate the overwhelming field effect on carrier hopping in the band tail regions of a-Si:H. Considerably higher fields have to be applied in the case of hole transport than electron transport to achieve comparable conductivities; this is discussed on the basis of the different tail state distributions and localization lengths.
Transient Forward Bias Response of Amorphous Silicon P-I-N Diodes
Authors: Street R. A. , Hack M. 
Published: March 2011

ABSTRACTWhen a forward bias is applied to an amorphous silicon p-i-n diode, there is a delay in the onset of the current. We present experimental data and numerical calculations, showing that the effect is due to trapped space charge which inhibits the onset of a double injection current. The dependence of the delay time on defect density, bias, illumination and the location of the defects is examined.
Reverse Recovery and Decay of Stored Excess Carriers in a-SI:HP-I-N Diode
Authors: Han Daxing , Wang Keda , Silver Marvin 
Published: March 2011

ABSTRACTCarrier transport properties, including mobility and carrier lifetimes, or the mobility-lifetime-product, are important parameters for the understanding of the electronic properties of amorphous silicon devices. We have attempted to study these parameters by the junction recovery method which is useful in crystal p-i-n devices, and by the decay of the forward and reverse bias current with varying periods of zero bias delays after removal of the forward bias. We found that the current decay by the standard reverse bias recovery is much faster than that due to the decay under zero bias. In this paper we present our experimental results. We conclude that the true decay of the stored charged due to forward bias is much longer and consequently, the stored charge is much larger than that suggested by standard reverse recovery experiments.
Room Temperature Recovery of Light Induced Degradation in A-SI:H Solar Cells
Authors: Fischer D. , Pellaton N. , Keppner H. , Shah A. , Fortmann C. M. 
Published: March 2011

ABSTRACTHigh intensity light-soaking and post-degradation room temperature recovery of single junction a-Si:H solar cells were investigated. After high intensity short term light-soaking, it was found that the degraded state was itself not stable. In the dark, fast degraded samples improved with time, even at room temperature. Two different sets of samples showed recovery rates in the range of 1 % gain of relative efficiency per hour. Recovery kinetics were the same in the dark and under low intensity carrier generation. Continued high intensity light soaking resulted in a steady decrease of the recovery rate with time. To explain this behavior, we suggest the presence of a non-electronic, slow process related to lattice reconfigurations that lock-in the light-induced defect states.
Quantum Efficiency of Textured a-Si:H P-I-N Solar Cells After High Intensity Light-Soaking
Authors: Li X. R. , Wagner S. , Bennett M. , Fonash S. J. 
Published: March 2011

ABSTRACTWe studied the effect of high-intensity light-soaking on the quantum efficiency spectrum of textured a-Si:H solar cells. We report experimental results on the time, temperature, and soaking light intensity dependence of the quantum efficiency (QE) measured in short circuit. Under 3Wcm-2 of white light the QE saturates after 30 minutes. The QE decays little in the blue and strongly in the red. The higher the temperature of saturation, the smaller the decay of the QE.
Evaluation of the Dice Method as A Tool For Amorphous Silicon Solar Cell Optimization
Authors: Von Der Linden M. B. , Schropp R. E. I. , Stammeijer J. G. F. , Van Der Weg W. F. 
Published: March 2011

ABSTRACTInformation about the spatial collection efficiency in a-Si:H solar cells is obtained from the Dynamic Inner Collection Efficiency (DICE) technique. With this non-destructive method single junction solar cells with efficiencies up to 10 % have been analysed under operating conditions. The influence of i-layer deposition parameters, such as the temperature and deposition time, on the spatial collection efficiency have been investigated. Deposition parameters for the i-layer have a large influence on the collection from the first 100 nm from the p+/i-interface. A higher i-layer deposition temperature or a longer deposition time results in a higher internal collection efficiency at a depth of 70 nm into the i-layer. Also results of DICE experiments on various textured TCO substrates are presented.
Kink Effect in Short Channel a-Si:H Thin-Film Transistors
Authors: Fortunato G. , Mariucci L. , Mattacchini A. , Pecora A. 
Published: March 2011

ABSTRACTAn avalanche increase of the drain current for high source-drain voltage (commonly called “kink effect”) has been observed for the first time in short-channel amorphous silicon thin-film transistors, fabricated using electron-beam lithography. This effect, caused by generation mechanisms at the drain junction, has been shown to be not only field but also temperature enhanced. The Frenkel-Poole mechanism is proposed in order to explain the data.
HF/Ethanol Preoxidation Silicon Cleaning: Analysis of the Silicon Surface and of the Ultra-Thin Oxide Layer
Authors: Garrido B. , Gessinn F. , Prom J.L. , Morante J.R. , Samitier J. , Sarrabayrouse G. 
Published: March 2011

ABSTRACTThe HF/Ethanol cleaning treatment is analyzed in comparison to the HF/H 20 one. The surface analysis is made on <100> silicon wafers with sacrificial oxide layer and silicon wafers with different crystallographic orientation without sacrificial layer. The results deduced from Atomic Force Microscopy, X-ray Photoelectron Spectroscopy and ellipsometry, show that siliconfluorine bonds are related with reactive sites. The structure of the thermally thin oxide layer grown after both cleanings has been analyzed and the electrical measurements show better performance for the HF/Ethanol cleaning.
Surface Cleaning and Passivation for the Growth of Si/Oxide/Si Structures
Authors: Wang Kun—Chih , Hwang Huey—Liang , Kung Chung—Yuan , Yew Tri—Rung 
Published: March 2011

ABSTRACTThis paper presents the results of surface cleaning and passivation of Si and oxide surfaces for the growth of Si/oxide/Si structures. Silicon surfaces are cleaned by the spin—etch process prior to the growth of silicon oxide. A silicon layer is then deposited after subsequent surface cleaning and chemical treatment on the surface of oxide/Si. Both the oxide and the silicon layers are grown in a plasma enhanced chemical vapor deposition system. The interface structure between layers of deposited Si/oxide/Si are observed by cross—section transmission electron microscopy (XTEM).
KOH-ETCH Related Defects on Processed Silicon Wafers
Authors: Kassel Laurent E. 
Published: March 2011

ABSTRACTKOH, an anisotropic etchant of monocrystalline Si, may cause roughness and defects whose shapes are related to crystallographic orientations. This paper studies the effect of processing steps on the formation of geometric etch defects. Implantation, thermal treatment, epitaxial growth or photoresist were not the source of such defects. In the scope of this study, only unwanted damage caused geometric etch defects. This makes the observation of the wafer after KOH etch a good indicator of the quality of previous steps.
Photo-Excited Cleaning of Silicon with Chlorine and Fluorine
Authors: Ito T. , Sugino R. , Sato Y. , Okuno M. , Osawa A. , Aoyama T. , Yamazaki T. , Arimoto Y. 
Published: March 2011

ABSTRACTChlorine radicals generated with UV irradiation are effectively used to remove residual metal contaminants after vatious LSI processes. Aluminum, iron, and copper atoms are effectively removed as volatile chloride species from silicon surfaces. The mechanism has been studied using silicon wafers intentionally contaminated with those metal ions. Contaminants are involved in native oxides as metal oxides or hydroxides. Chlorine radicals penetrate the native oxides and attack those oxides or hydroxides vaporizing metal chlorides. The cleaning process is accompanied with slight etching of silicon surfaces to a depth as thin as a few nm. However, this is not essential because the substrate temperature is more important than the etching depth. Alkaline metals are also removed from the surfaces to the level as small as the detection limit of atomic absorption spectroscopy. We believe that those are removed through a lift-off process. The, wixture of fluorine and hydrogen gases removes a native oxide of silicon under UV irradiation. Hydrogen fluoride radicals react with native oxide resulting in hydrogen termination on silicon dangling bonds. These cleaning processes are advantageous for low temperature silicon epitaxy, reliable contact formation, and thin gate oxide growth.
Plasma-Surface Interaction Limits for Remote H-Plasma Cleaning of Si(100)
Authors: Schneider T.P. , Bernhard B.L. , Chen Y.L. , Nemanich R.J. 
Published: March 2011

ABSTRACTAn investigation of the parameters in H-plasma cleaning influencing H-diffusion and surface etching is described. The Si surface and subsurface regions were characterized with Raman spectroscopy and high resolution transmission electron microscopy (HRTEM), and the plasma parameters were monitored with a double Langmuir probe and optical emission spectroscopy. The parameters varied in the rf plasma cleaning were the substrate temperature, the rf power, and the plasma exposure time. It was found that low pressure and low power H-plasma exposure was effective in terms of cleaning the surface. In the 300°C, 20 Watts, 2 min. H-plasma exposure case, the Raman spectra indicated that there was no detectable H incorporation into the Si bulk and HRTEM showed no obvious defect microstructure in the near surface region and that the surface was smooth. In contrast, in the 150°C, 50 Watts, 60 min. H-plasma exposure case, HRTEM indicated that H-induced platelet defects formed in the Si(100) subsurface region and that the surface morphology was rough. Raman scattering revealed Si-H features at ∼2100 cm−1.
Double Beam Photoconductivity Modulation System and its Application to the Characterization of a Process of Photoresist Removal
Authors: Usami A. , Fujiwara H. , Nakai T. , Matsuki K. , Takeuchi T. , Wada T. 
Published: March 2011

ABSTRACTA laser/microwave method using two lasers of different wavelengths for carrier injection is proposed to evaluate near surface regions. These lasers are a He-Ne (wavelength=633nm, penetration depth=∼3μm) and a YAG lasers (wavelength=1060nm, penetration depth=∼500μm). Using a microwave probe, the amount of injected excess carriers can be detected. The carrier concentration is mainly dependent on the condition of the surface when carriers are excited by the He-Ne laser. It is mainly dependent on the condition of the bulk region when carriers are excited by YAG laser. We refer to microwave intensities detected by the He-Ne and the YAG lasers as the surface-recombination-velocity-related microwave intensity (SRMI) and bulkrelated microwave intensity (BRMI), respectively. We refer to the difference between SRMI and BRMI as relative SRMI (R-SRNI), which is closely related to the condition of surface and surface active region. We evaluate the near surface regions of the samples after plasma and wet etching for removing the photoresist layer. And we evaluate the near surface regions of the samples after a heat treatment which is done to recover the damage introduced by plasma etching. It is found that the R-SRMI method is better suited to near surface region evaluation than conventional lifetime measurements.
Sulfidation and Post-Sulfidatton Reactions on Gallium Arsenide
Authors: Yota J. , Burrows V. A. 
Published: March 2011

ABSTRACTChemical treatment of GaAs with sulfur-containing compounds has been shown to improve GaAs surface electronic properties. There is still considerable controversy, however, regarding the chemical nature of the surface film which results from the sulfidation, and of the basis of the electronic improvement and of the decay in the improved electronic properties with time. We have investigated the surface chemistry of the chemical sulfidation treatment of GaAs with Na2S.9H2O and (NH4)2S. Using surface infrared reflection spectroscopy (SIRS) and x-ray photoelectron spectroscopy (XPS), we have studied the GaAs surface and its behavior with time after such treatments. Results show that both of these sulfidation treatments removed the chemical oxide of GaAs, leaving behind a thin film on the surface. XPS results show that the Ga-O and As-O peaks were removed after treatment and that As-S and no Ga-S peaks were formed. Infrared results show that the film deposited after Na2S.9H2O treatment slowly reacted in air to form sodium carbonate and rhombic sulfur. In addition, this film contains compounds with sulfur-oxygen bonds, which most likely were arsenic sulfate, sulfite, and thiosulfate salts. The film deposited on the (NH4)2Streated GaAs surface was identified as ammonium thiosulfate and slowly decomposed with time. Rinsing with water removed the thin film formed after either sulfidation treatment.
The Passivation of Gallium Arsenide Surfaces with Selenium from Gaseous Sources
Authors: Gu G. Y. , Ogryzlo E. A. , Wong P. C. , Mitchell K. A. R. 
Published: March 2011

ABSTRACTTwo techniques were used to apply a thin layer of selenium to GaAs (100) surfaces: (a) the thermal decomposition of hydrogen selenide at 120°C, and (b) the deposition of gaseous selenium formed in the reaction of hydrogen atoms with H2Se. Angle dependent XPS measurements show that AsxSey, but not GaxSey, forms on the surface in both cases. This work therefore establishes a surface behavior for selenium on GaAs(100) which contrasts with that described earlier for sulfur on this surface.
S-Passivated InP Surfaces Prepared by (NH4)2S Treatments
Authors: Tao Y. , Yelon A. , Sacher E. , Lu Z.H. , Graham M.J. 
Published: March 2011

ABSTRACTS-terminated InP(100) surfaces which are chemically clean and stable were obtained by sulfide solution treatments. X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) were used to investigate the thermal and chemical stability of the surfaces. Schottky diodes based on S-passivated InP(100) wafers were used as test devices tostudy the surface electrical properties.