bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical Analysis of Sweep-Out Experiments in Doped Hydrogenated Amorphous Silicon Films
Authors: Silver Marvin , Branz Howard M. , Adler David 
Published: March 2011

AbstractWe analyze the transient response of i/n/i and i/p/i semiconductor structures in terms of space-charge-limited and emission-limited currents. In this ‘sweep-out’ experiment, an initial space-charge-limited current governed by the i-layer characteristics gives way at later times to an emission-limited current from the doped layer. The emission-limited current response can be used as a new spectroscopy for determining the electronic density of states near the mobility edge of doped semiconductors. We summarize the published experimental sweep-out data and draw conclusions about the density of electronic states of both n-type and p-type hydrogenated amorphous silicon.
Experimental Study of Sweep-Out in N-Type Hydrogenated Amorphous Silicon
Authors: Winborne G. , XU L. , Silver M. , Branz H. M. 
Published: March 2011

AbstractExperimental results on the temporal response of i/n/i hydrogenated amorphous silicon structures are presented as a function of voltage. The current is initially space charge limited followed by a transition to an emission limited current. The data generally exhibits four subsequent time dependence regimes e.g. :(1) an exponential decay, (2) followed by a t−2 decay, (3) then a t−1 decay and (4) lastly a t(α−1) decay where α<1. The current versus time allows one to derive a density of states. The deduced density of states in the arsenic doped n layers displays a peak at shallow energies followed by an exponential with an energy decay constant of approximately 300°K followed by a flat region and finally followed by a slowly rising density of states. The initial Fermi level is estimated to be within the peak located less than 0.3eV from the mobility edge.
Phosphorus and Boron Doping of a-Si:H Effects of Deposition Temperature
Authors: Pruppers M. J. M. , Maessen K. H. M. , Bezemer J. , Habraken F. H. P. M. , van der Weg W. F. 
Published: March 2011

AbstractHeavily phosphorus and boron doped hydrogenated amorphous silicon films were deposited in the temperature range 50 to 300 °C. Concentrations of P, B and H, IR spectra and room temperature conductivity have been measured. When the deposition temperature is raised from 50 to 300 °C the concentration of P increases, while the concentration of B decreases. The dark conductivity of both P and B doped films decreases dramatically when the deposition temperature is lowered. We interpret these results on the basis of assumptions concerning the microstructure of the deposited films, and especially the variation of this structure with deposition temperature.
Effect of Low Level Doping of Boron and Phosphorus on the Properties of Amorphous Silicon Films
Authors: Tran N. T. , Epstein K. A. , Grimmer D. P. , Vernstrom G. D. 
Published: March 2011

AbstractEffect of low level doping of boron and phosphorus on the properties of amorphous silicon films (a-Si:H) was studied. Doping level of both boron and phosphorus was in the range of 1017 atoms/cm3. Apparent improvement in the stability of dark and photoconductivity of a-Si:H films upon low level doping does not result from the elimination of light-induced defects. The stability of the dark and photoconductivity upon doping is an indication of pinning of the Fermi level.
NMR Investigation of the Local Dopant-Hydrogen Configuration in Amorphous Silicon
Authors: Ready S. E. , Boyce J. B. 
Published: March 2011

AbstractHydrogen's role in the doping efficiency and long term stability of hydrogenated amorphous silicon is not well understood. The introduction of dopants has been observed to cause an increase in the deposition rate and in the formation of dangling bonds. We have performed NMR spin echo double resonance measurements on heavily doped amorphous silicon samples prepared via plasma deposition in order to ascertain the dopanthydrogen structural units. The resulting dopant concentrations were 2.0 and 0.5 at. % boron and/or phosphorus in compensated and singly doped material respectively. Our results indicate no direct dopant-hydrogen bonding in the compensated or n-type samples. However, in the p-type material the data indicate that approximately 40% of the boron atoms are directly bonded to a hydrogen.
Possible Diffusion of Molecular Hydrogen Along Microvoids in Device-Quality a-Si:H
Authors: Vanderheiden E. J. , Ohlsen W. D. , Taylor P. C. 
Published: March 2011

AbstractA comparison of 1H nuclear magnetic resonance (NMR) measurements in freshly prepared a-Si:H films on substrates with those removed from the substrates shows that a large fraction of the trapped H2 molecules are released when the films are removed from the substrates. After the films on substrates have been aged for several months, an equal amount of H2 has diffused out of the film. This gradual aging appears-to stabilize after several months. Once aged, H2 can be diffused into the films by immersion in H2 gas. The diffusion time is around 2 weeks at 300 K which is much slower than in vitreous quartz or 7059 glass at the same temperature. Diffusion, which is enhanced during the aging process, could proceed via the remnant columnar structure in the film. This speculation is supported by the inability to detect, using pake-doublet experiments, significant changes in the H2 content and by the recent observation of oxygen diffusion along remnant columnar structure in device quality films.
Hydrogen Diffusion in Undoped a-Si:H
Authors: Chou S. F. , Schwarz R. , Okada Y. , SLOBODIN D. , Wagner S. 
Published: March 2011

AbstractWe measured the diffusion coefficient of H in a-Si:H between 36°C and 690°C via H2-evolution and the pressure rise in a closed ampoule. Our measurement temperatures reached ∼110°C above the highest T reported to date. The diffusion coefficient for unalloyed a-Si:H, DH=1.66×10−3 exp [−1.45 eV/kT] cm2 s−1, agrees with the earlier, lower-T, measurements. Between 250°C and 690°C the H-diffusion mechanism in a-Si:H appears to remain the same, with DH ranging from 10−17 cm2s−1 to 10−10cm 2s−1.
Composition Oxidation and Chemical Etching Properties of a New Amorphous Silicon-Boron Thin Film
Authors: Tong B. Y. , Wong S. K. , Yao J. , Lau W. N. , Du N. , John P. K. 
Published: March 2011

AbstractWhen silane, with more than 0.1% of diborane in the gas mixture, are co-pyrolyzed at temperatures below 540°C, an amorphous silicon-boron alloy is formed. The composition of the solid film was determined by SINS and Auger spectroscopy. The amorphous nature of the films was established by X-ray diffraction, laser Raman spectroscopy, and TEM electron diffraction. Electrical and optical properties of this material are reported. Oxidation and chemical etching of this material were also studied.
Quantitative Measurement of Hydrogen Content in a-Si:H by Ar+ Excited Auger.
Authors: Farias M. H. , Hirata G. A. , Cota-Araiza L. , Galvan D. H. , Asomoza R. 
Published: March 2011

AbstactHydrogenated amorphous silicon (a-Si:H) is well known by its applications for solar energy conversion devices in a large scale. Hydrogen has the capability of terminating the dangling bonds in the amorphous silicon structure and improves the optical properties for effective utilization of the solar spectrum. With this, the quantification of the hydrogen content in a-Si:H is an important task in its characterization.Auger electron spectroscopy induced by Ar+ ion bombardment (IAES) has been shown to be sensitive to the presence of hydrogen in a-Si:H [1,2]. The Si-L 2VV peak has a distinctively new shape as compared to electron- xcited. Auger were only some slight differences can be observed [3]. contribution to the IAES to that particular peak coming from de-excitations inside and outside the solid can be identified [4].In this work, IEAS of the Si-L23VV peak were obtained for a-Si:H prepared by glow discharge, grystalline silicon, and crystalline silicon implanted with silicon ions. The relative differences in the spectra are characterized. In particular the changes in the relative amplitudes of the so-called “bulk-like” peak to the “atomic-like” peak as a fuction of hydrogen content are obtained.
Comparison of Properties of a-Si1−x Gex:H and a-Si1−x Gex:H:F
Authors: Mackenzie K. D. , Paul W. 
Published: March 2011

AbstractThe structural, electrical and optical properties of amorphous Si-Ge alloys prepared either from mixtures of hydrides or of fluorides will be compared. It will be shown that the majority of many properties studied are essentially the same, the major exceptions being the structure of thin films used for TEM investigation, and the photocurrents developed between contacts in a coplanar configuration. Possible explanations for the result of including fluorine in the preparation plasma will be discussed.
Structural, Optical, and Electrical Properties of Amorphous Hydrogenated Carbon Nitride
Authors: Han He-Xiang , Feldman Bernard J. 
Published: March 2011

AbstractAmorphous hydrogenated carbon nitride thin films have been grown by plasma decomposition of a feedstock of CH4 and N2. In the films with higher nitrogen concentration, the infrared absorption spectra are dominated by NH2 modes and give strong evidence of a polymeric structure. The optical absorption and photoluminescence spectra show that nitrogen incorporation decreases the bandgap and increases the structural order of these thin films. The undoped material is an insulator with resistivities up to 1015Q cm, but when doped with iron, it becomes a p-type degenerate semiconductor.
Determination of Interface and Surface Structure During the Growth of a-Si:H-Based Heterostructures
Authors: Collins R. W. , Cavese J. M. 
Published: March 2011

AbstractEllipsometry measurements of hydrogenated amorphous silicon (a-Si:H)-based heterostructures have been used to characterize surfaces and single interfaces. From spectroscopic studies before and after plasma oxidation of a-Si:H, surface roughness on the atomic scal; (in the plane of the surface) can be distinguished from larger scale (> 100 Å) modulation. We also show how in situ studies of heterostructure preparation can be used to set deposition conditions to minimize near-interface layers owing to thickness dependent film properties. When these are eliminated, the discrepancies in the data from planar layer-bylayer growth models can be attributed to the larger scale surface and interface modulation. Finally, extensive deviations from planar growth for a-Si:H/μc-Si:H have been characterized in terms of specific heterogeneities.
a-Si:H TFT Driven Linear Image Sensor
Authors: Ito H. , Suzuki T. , Nobue M. , Nishihara Y. , Sakai Y. , Ozawa T. , Tomiyama S. 
Published: March 2011

AbstractA new contact type linear image sensor, which has 8.5 inches in length and 300 dot/inch, has been developed. By using a thin film transistor (TFT) array as a switching device, it requires only one IC chip compared with 20 ICs in conventional sensor.The new sensor integrates a-Si:H photodiode (PD) array, a-Si:H TFT array, multiplex circuits and an analog multiplexer on a single substrate. The TFT has an inverted staggered structure and amorphous silicon nitride (SiNx) is used as a gate insulator. The PD has a Cr/a-Si:H/ITQ sandwich structure and each PD is completely isolated by photolithography. In the multiplex circuits, a ground line is inserted between each signal line to reduce a capacitive coupling between them.A new custom LSI has also been developed. It has 64-ch input terminals to detect small signal with amplification and 41-ch output terminals to control the gates of TFT array. The sensor with the new LSI has achieved 2MHz clock frequency operation and proved to be used as a high speed device.
Physics of Novel Amorphous Silicon High-Voltage Transistor
Authors: Hack M. , Tuan H. , Shaw J. , Shur M. , Yap P. 
Published: March 2011

AbstractIn this paper we describe the operation of a novel amorphous silicon high voltage transistor. Its attractive feature is that it can operate at source-drain voltages in excess of 400 volts but its characteristics are controlled by applying only a low bias (0-10 volts) to a gate electrode covering a small portion of the sourcedrain channel near to the source. The portion of the device over this gate electrode operates as a conventional amorphous silicon Field-Effect Transistor which injects electrons into the intrinsic amorphous silicon between this region and the drain electrode. We present experimental data showing the current-voltage characteristics of this new transistor as a function of geometry and demonstrate that the above model realistically describes its operation.
Amorphous Silicon Thin Film Transistor Array Technology: Applications in Printing and Document Scanning
Authors: Weisfield R. L. , Tuan H. C. , Fennell L. , Thompson M. J. 
Published: March 2011

AbstractAmorphous silicon (a-Si:H) thin-film transistor (TFT) array technology has been developed for new applications in low-cost, high-quality electronic printing. We have fabricated page-wide arrays of low-voltage pass transistors using a-Si:H TFTs for ionographic printing, in which voltages of 0 to 15 volts applied to a line of output electrodes modulate the flow of ions charging a dielectric receptor. High-voltage a-Si:H TFTs have been used in an electrographic printer to modulate high voltages required to initiate air discharges. Combining a-Si:H photodiodes on TFT arrays, we have also designed circuits for document scanning and photosensor amplifiers. TFT performance in relation to these novel printer and sensor applications will be discussed. Issues related to process integration, circuit design, and large-area fabrication technology will be addressed.
Radiative Recombination in a-Si:H-FETs
Authors: Carius R. 
Published: March 2011

AbstractWe have studied the photoluminescence in the space charge region of field effect transistors (FETs) based on a-Si:H in the temperature range T>100K. The radiative recombination rate rises with increasing gate voltage (Vg >0) The increase is more pronounced at the high energy side of the photoluminescence spectrum and the relative changes increase with temperature. These results are compared to those obtained on doped a-Si:H films, where the defect photoluminescence band increases slightly with increasing doping level but the intrinsic band drops off very rapidly. The different influence of the Fermilevel shift in the doped films is explained by the increasing defect concentration which dominates the photoluminescence results. The results in the FETs are attributed solely to the changes in the occupation of the dangling bond states.
Undoped Amorphous Silicon TFTs with n-Channel OR p-Channel Device Operation for the Determination of the Gap States Distribution.
Authors: Schropp Ruud E.I. , Verwey Jan F. 
Published: March 2011

AbstractHydrogenated amorphous silicon thin-film transistors (TFTs) were made with either n-channel or p-channel device operation. Layers of undoped amorphous silicon were deposited in the same run and appropriate contact implantation techniques were used. These devices offer the possibility of investigating unipolar conduction of either electrons or holes. In this way ambiguities in the field-effect (FE) analysis of the density of states (DOS) can be avoided. We present the DOS distribution over the entire band gap region of undoped amorphous silicon deduced from a pair of transfer characteristics (one forward and one in reverse). Both types of TFTs are subject to degradation under continuous accumulation conditions. The rate of current decay under hole accumulation appears to be larger than under electron accumulation, as is expected from the width of the respective tail-states distributions. The ON/OFF current ratios obtained for the p- and n-channel devices were 105 and 107, respectively, and both devices showed good pinchoff behaviour. Therefore, these devices are in principle attractive for application in novel amorphous silicon integrated logic circuits (IC).
Progress in Tandem PV Power Modules
Authors: Gay Charles F. , Mitchell K. W. 
Published: March 2011

AbstractAdvances in materials research continue to push forward the performance of thin film photovoltaic technology and bring closer to reality the goal of low cost (less than $2/wattpeak selling price), high efficiency (greater than 15%) modules. A tandem module of thin film silicon:hydrogen alloy (TFS) above copper indium diselenide (CIS) promises to be a most effective approach to this goal. The performance of the high band gap TFS and low band gap CIS has been advanced in part by understanding the nature of the materials and by optimizing the processing techniques. Careful evaluation of various alternatives has led to the selection of suitable materials to serve as the transparent conductive electrodes and the transparent optical coupler between the TFS and CIS. This paper addresses the next steps in capturing efficiency improvements and characterizes probable real world performance.
Determination of the Efficiency Enhancement Due to Scattering from Rough TCO Contact for a-Si:H P-I-N Solar Cells
Authors: Walker C. , Hollingsworth R. E. , Madan A. 
Published: March 2011

AbstractA-Si:H p-i-n solar cells were deposited on textured transparent conducting oxide coated glass substrates to experimentally determine the enhancement in the short circuit current density. It was found that the optical thickness can be increased by a factor from 3 to 5. These results agree reasonably well with the predictions of optical enhancement theory.
Radiation Resistance of Amorphous Silicon Alloy Photovoltaic Cells
Authors: Woodyard James R. , Hanak J. J. 
Published: March 2011

AbstractThe results of investigations of high energy proton radiation resistance of a-Si alloy thin film photovoltaic cells are reported. Irradiations were carried out with 200 keV and 1.00 MeV protons with fluences ranging between IEII and IEl5 cm-2. Defect generation and passivation mechanisms were studied using the AM1 conversion efficiency and isochronal anneals. It is concluded that the primary defect generation mechanism results from the knock-on of Si and Ge in the intrinsic layer of the cells. The defect passivation proceeds by the complex annealing of Si and Ge defects and not by the simple migration of hydrogen.
Effects of Silicon:Carbon P+ Layer Interfaces on Solar Cells
Authors: Jeffrey F. R. , Vernstrom G. D. , Weber M. F. , Gilbert J. R. 
Published: March 2011

AbstractResults are presented showing the effects on amorphous silicon (a-Si) photovoltaic performance of the interfaces associated with a silicon carbide (a-Si:C) p+ layer. Carbon grading into the intrinsic layer from the p+ layer increases open circuit voltage (Voc) from O.7V to 0.88V. This effect is very similar to the boron profile effect reported earlier and supports the contention that Voc is being limited by an electron current at the p-i interface. The interface between the p+ a-Si:C layer and the transparent conductive oxide (TCO) is shown to be a potential source of high series resistance, with an abrupt interface showing the most serious problem. The effect is explained by electron injection from the TCO into the p+ layer being inhibited as a result of band mismatch.
Effects of Carbon Grading at the p/i Interface on the Open Circuit Voltage of p-i-n and n-i-p Amophous Silicon Solar Cells
Authors: Tran N. T. , Jeffrey F. R. , Olsen D. J. 
Published: March 2011

AbstractCarbon grading in the buffer layer at the p/i interface increases the open circuit voltage of both p-i-n and n-i-p amorphous silicon solar cells. We propose that carbon grading enlarges the electric field and reduces the electron tunneling at the p/i interface.
Stability in Amorphous Silicon
Authors: Smith Z E. , Wagner S. 
Published: March 2011

AbstractThe experimental phenomena associated with light-induced degradation and thermal recovery of hydrogenated amorphous silicon (a-Si:H) films are reviewed, with special emphasis on the limitations of each experimental technique. When several techniques are used in concert, a fuller picture emerges. Recent experiments suggest different positions in the band-gap of the paramagnetic-associated defect states (the dangling bonds) for doped and undopedfilms; this information can be combined with conductivity, sub-bandgap optical absorption and electron spin resonance data to yield a model for the density of gap states (DOS) in a- Si:H, including how the DOS changes upon illumination and annealing.
Degradation Behavior of a-Si:H Pin Solar Cells With Intentionally O-Contaminated i-Layers
Authors: Krühler W. , Gonzel E. 
Published: March 2011

AbstractThe discussion about the influence of oxygen on the degradation be-havior of a-Si:H pin solar cells is now as before controversial. Therefore, we prepared a-Si:H pin solar cells having different amounts of O contami-nation in the i-layer by adding O2 gas to the silane gas during the glow-discharge deposition of the i-layer. The admixture of O2 gas was in the 0 ppm to 1000 ppm range resulting in an O concentration in the i-layer of 1.10190/cm3 to 3.1020 0/cm3 determined by SIMS measurements. Then we inves-tigated the long-term degradation behavior of these cells, exposing them for about 270 h to white light of 100 mW/cm2 intensity. During the first 20 h the cell efficiencies dropped relatively fast to about 80 % of the initial value and then more slowly to about 60 % after 270 h. The degradation of the cells may be slightly different during the first 20 h, but this has nothing to do with the O concentration. The normalized efficiency values meet all at the 60 % level after the long-term light exposure for 270 h. We there-fore conclude that the degradation behavior of pin a-Si:H solar cells after long-term exposure is not dependent on the O concentration in the range investigated. At O concentrations higher than about 5.1020 cm−3, the den-sity of states increases rapidly and the electrical properties of the solar cells deteriorate, making it difficult to clarify the true influence of oxygen on the degradation behavior.
Amorphous Silicon Alloy Punch-Through Diodes for Display Applications
Authors: den Boer W. , Guha S. , Kawasaki A. , Yaniv Z. 
Published: March 2011

AbstractThe current-voltage characteristics of amorphous silicon alloy n-π-n and p-i-p diodes have been investigated. These diodes show highly nonlinear conduction characteristics which are attributed to the punch-through effect. The dependence of the non-linearity on the thickness and doping of the intermediate active layer support this interpretation. An experimental 108 × 108 pixel liquid crystal display was built with punch-through diodes as pixel switches.
Transient Photoresponse of Amorphous Silicon p-i-n Diodes
Authors: Deimel P. P. , Moller G. , Baumeister K. 
Published: March 2011

AbstractAmorphous silicon p-i-n diodes were illuminated with LED-generated trains of rectangular light pulses under various duty-cycle conditions. Our results indicate that such diodes are able to handle modulation rates in excess of 10MHz over a wide range of operating temperatures. Measurements of the dark I-V characteristics show that the shot-noise in properly designed junctions can be reduced to a level comparable to c-Si photodiodes.
Quantum Effect Device Using Disordered Surface in Doped Si Near the Metal-Nonmetal Transition
Authors: Ochiai Y. , Yoshizaki R. , Matsuura E. 
Published: March 2011

AbstractWe have observed several steps in the I-V characteristics of nonmetallic Sb doped Si near the metal-nonmetal transition. The steps appear at equal intervals in the bias voltage of the low temperature I-V curve and the intervals in the voltage are independent on magnetic field. Such strongly nonlinear conduction can be explained by neither the Joshphson junction effect nor the Stark ladder effect. We have compared it with tunneling models in order to study a new application to a current or a voltage standard using quantum effect transport.