bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Characterization and Optical Modelling of Absorption and Light Trapping in a-Si:H Solar Cells on Textured Tco
Authors: Leblanc François , Perrin Jérâme , Cornil Elizabeth. , Schmitt Jacques 
Published: March 2011

ABSTRACTThe quantitative description of the optical phenomena occuring in a-Si:H solar cells on textured substrates is a key issue to maximize the photovoltaic conversion efficiency. A semi-empirical numerical model is proposed taking into account the scattering induced by roughness at each interface of a multilayer structure. The scattered reflected and transmitted components are added to a classical matrix treatment of specular components. For each scattering angle, a new source beam is tracked in the subsequent layers. Light polarization and interference effects are properly taken into account and the energy deposited in each layer is derived. The model is tested on various structures and on a-Si:H p-i-n solar cells by angular-resolved reflectance and transmittance measurements and photothermal deflection spectroscopy.
Film and Solar Cell Properties of a-SiC:H Alloys
Authors: Li Yuan-Min , Catalano A. , Fieselmann B.F. 
Published: March 2011

ABSTRACTHydrogenated amorphous silicon-carbon alloys (a-SiC:H) with 1.9–2.0 eV bandgaps have been grown by glow-discharge using methane as the source of carbon with high hydrogen dilution (CH4+H2) at various substrate temperatures. A thickness dependence of the properties of un-doped films is observed. The photo-electronic properties have been much improved in these undoped alloys compared to those of CH4 based films without H-dilution, however the CH4+H2 based boron doped a-SiC:H films show little improvement. Simple p-i-n single junction solar cells using improved wide-gap a-SiC:H Mayers, based on the CH4+H2 recipe and the novel carbon feedstock trisilylmethane (TSM), show high open circuit voltages and high fill factors. The cell stability under illumination has been tested. There is no correlation in degradation rates between the a-SiC:H cell efficiency and the photoconductivity of the corresponding i-layer films.
Effect of Boron and Phosphorus Ion Implantation on a-SixC1-x:H Thin Films
Authors: Demichelis F. , Galloni R. , Pirri C. F. , Rizzolid R. , Summonte C. , Tresso E. 
Published: March 2011

ABSTRACTIon implantation of boron and phosphorus in device quality a-SixC1-x:H films deposited by Ultra High Vacuum Plasma Enhanced Chemical Vapor Deposition (UHV PECVD) has been performed. The effects of damage and of damage recovering after annealing were investigated by optical absorption, electrical conductivity and infrared (IR) spectroscopy measurements. It is found that samples doped by phosphorus implantation can have dark conductivities as high as those obtained on samples doped with boron, either by ion implantation or gas phase.
Transient Leakage Currents in Amorphous Silicon Thin-Film Transistors
Authors: Hack M. , Steemers H. , Weisfield R. 
Published: March 2011

ABSTRACTIn this paper we present both experimental data and computer simulations of the leakage characteristics of amorphous silicon (a-Si) thin film transistors operated under time transient conditions. The transient behaviour of these devices for realistic operating conditions is often very different from their steady-state characteristics, due to the slow response of deep traps in a-Si. Our model is in good agreement with the data and realistically accounts for the time-dependent behaviour of amorphous silicon with leakage being mainly determined by a combination of fixed charge in the passivation dielectric and a distribution of surface states at the top silicon interface. We show how voltage pulses applied to the gate of a TFT affect its performance as a pixel switch in a two-dimensional array. In particular we concentrate on the effects of light and bias stressing.
Low-Resistivity Amorphous Silicon for Contacts Using Low-Temperature Rapid Thermal Annealing
Authors: Knoch Lynnita , Tam Gordon , Theodore N. David , Pennell Ron 
Published: March 2011

ABSTRACTFabrication of SiGe heterojunction bipolar transistors (HBTs) requires a low thermal budget to avoid relaxation of the strained SiGe base layer. Ion implantation is one of the most widely used techniques to achieve contacts. However, due to thermal budget constraints, low temperature rapid thermal annealing (RTA) cycles to activate these implants are insufficient to anneal out all of the implant damage. Polysilicon contacts provide an alternative to ion implantation, but are typically annealed at high temperatures (>950°C) to achieve low sheet resistivity. In this study, amorphous silicon and polycrystalline silicon films were implanted with boron, arsenic, or phosphorus and RTA'd at temperatures from 800°C to 950°C and compared to single crystal silicon with identical implants and RTA cycles. The films were characterized using four-point probe, Hall measurements, TEM (transmission electron microscopy), and SIMS (secondary-ion mass-spectrometry). TEM analysis shows that the amorphous deposition produces larger grains upon RTA due to more rapid grain growth than the polycrystalline deposition. The sheet resistance for the amorphous deposited films is much lower than that of the polycrystalline deposition for all implant conditions. Activations of the implants indicate that the arsenic and phosphorus segregate to the grain boundaries, while the boron does not. The segregation is more significant for the polycrystalline films than for the amorphous films and can be explained by the grain boundary area. For contacts to the SiGe HBT, which requires a low thermal budget, an amorphous deposited silicon film is advantageous over a polycrystalline film at low annealing temperatures because it has lower sheet resistance, less segregation to the grain boundaries, and produces larger grains.
A New Model for Series Resistance of Amorphous Silicon Thin Film Transistor
Authors: Kim Yong S. , Park Jin S. , Lee Seong K. , Hwang Jung R. , Choi Hong S. , Choi Yearn I. , Han Min K. 
Published: March 2011

ABSTRACTWe presents a new model for the series resistance of an amorphous silicon (a-Si) thin film transistor (TFT) with an inverted-staggered configuration, considering the current spreading under the source and the drain contacts as well as the space charge limited current. The calculated results of our model have been in good agreements with the measured data over a wide range of applied voltage, gate-to-source and gate-to-drain overlap length, channel length, and operating temperature. Our model shows that the relative contribution of the series resistances to the current-voltage (I-V) characteristics of the a-Si TFT in the linear regime is more significant at low drain and high gate voltages, for short channel and small overlap length, and at low operating temperature, which has been verified successfully by the experimental measurements.
A New Narrow Width Effect in Amorphous Silicon Thin Film Transistors
Authors: Martin Russel A. 
Published: March 2011

ABSTRACTA new narrow width effect is described for a-Si thin film transistor, TFT, having the inverted staggered structure with source and drain contacts overlapping the edge of the island passivation nitride. In this structure, where the source and drain contacts overlap the edge of the island they contact the a-Si and make a segment of channel effectively shorter. The edges thereby contribute a greater amount to the total drive current, and as width decreases, that fraction increases; what is therefore seen is a channel length effect masquerading as a width effect.The results of measurements down to a width of 3um are given and the effective region of enhanced current is estimated. A SPICE model is presented that allows a simple representation of this effect.
Ion Channeling and Spectroscopic Ellipsometry Examinations of Thin-Film SiO2 /EPI-Si(001) Structures
Authors: Fiory A. T. , Roy P. K. , Jellison G. E. 
Published: March 2011

ABSTRACTRutherford backscattering ion-channeling spectrometry (RBS) and 2-channel spectroscopic polarization modulation ellipsometry (2-C SPME) were combined in a study of 3- to 16-nm SiO2 films to discern possible differences between conventional MOS oxides, modified surface preparation, and stacked-oxide processes which combine chemical vapor deposition with furnace oxidation. An excess silicon scattering is observed by RBS, which suggests atomic displacements associated with interfacial roughness and strain in the crystalline Si. Ellipsometry observes an increase in refractive index with decreasing film thickness, which is consistent with interfacial roughness or Si strain. The various preparation methods for device-quality MOS oxides yielded essentially equivalent results and film densities close to bulk, fused SiO2.
VPD/SIMS Measurement of Surface Al on Silicon Substrates
Authors: Chia V.K.F. , Odom R.W. , Bleiler R.J. , Sams D.B. , Hockett R.S. 
Published: March 2011

ABSTRACTAn experimental protocol using secondary ion mass spectrometry to measure Al in vapor phase decomposition (VPD) solutions has been developed to achieve a detection limit of 108 atoms/cm2. The analytical technique is called VPD/SIMS. The procedure utilizes sample preparation techniques developed for microvolume SIMS. Preliminary SIMS analysis of simulated VPD solutions consisting of dilute HF indicate that a theoretical detection limit of 5.7×105 Al atoms/cm2 is possible from a 6″ wafer.
Kinetics of UV/O2 Cleaning and Surface Passivation: Experiments and Modeling
Authors: Bedge Satish , McFadyen Joseph , Lamb H. Henry 
Published: March 2011

ABSTRACTRemoval of adsorbed organic contaminants from Si surfaces by reaction with molecular O3 and photo-generated atomic oxygen species in a UHV-compatible photochemical reactor was investigated. Treatment of contaminated wafers with externally generated O3 at 25°C was effective in removing adsorbed organics, but surface cleaning rates were enhanced by simultaneous 254-nm UV irradiation of the reactor contents. In situ photo-generation of O3 and atomic oxygen species by 185- and 254-nm irradiation of O2 gave comparable results. A simplified gas-phase kinetics model describing O3 generation by a low-pressure Hg lamp was developed and used to gain insight into the effects of relative humidity and O2 partial pressure on steady-state O3 concentrations.
Surface Stability and Flow Characteristics of BPSG Film by N2O Plasma Treatment
Authors: Kim C.G. , Lee H.S. , Ahn Y.C. , Chung U.I. , Lee J.K. , Lee J.G. 
Published: March 2011

ABSTRACTBPSG films show good flow characteristics with the increase of boron and phosphorus concentration. As–deposited BPSG films with high boron and phosphorus concentration, however, have a dopant instability which results in film bursts, cracks, and precipitates, due to water absorption. Elimination of dopant instabilities of BPSG films by N2O plasma treatment is investigated. Film structure, composition and flow properties are evaluated by FT-IR, SIMS, and SEM, respectively. Dopant stability is examined after H2SO4 boiling. After H2SO4 boiling without N2O plasma treatment, BPSG films with high boron and phosphorus concentration show poor flow characteristics. Boron and phosphorus are leached out of the BPSG films by reaction with absorbed water during the H2SO4 boil. N2O plasma treatment results in a thin surface layer composed of Si-O-B bonds. These bonds do not dissolve in water. It is proposed that the thin layer consisting of Si-O-B bonds prevents the penetration of water into BPSG film during H2SO4 boiling.
Detection of Thin Interfacial Layers by Picosecond Ultrasonics
Authors: Tas G. , Stoner R. J. , Maris H. J. , Rubloff G. W. , Oehrlein G. S. , Halbout J. M. 
Published: March 2011

ABSTRACTWe report on experiments in which the picosecond ultrasonics technique is used to detect the existence of thin layers of CFx at the interface between a metal film (Al) and a silicon substrate. Acoustic vibrations are excited in the metal film when a picosecond light pulse is absorbed. The thickness of the CFx can be estimated from the rate at which these vibrations are damped out via transmission of sound into the silicon substrate through the CFx layer. We show that thin CFx layers can also be detected via their effect on the rate at which heat flows from the metal to the silicon.
The Wet Etching of CdZnTe Substrates for OMVPE Growth
Authors: Chan T.W. , Bao X.J. , Oh I.H. , Sides P.J. , Ko E.I. 
Published: March 2011

ABSTRACTThe etching of CdZnTe substrates by bromine-methanol solutions was studied by chemi-mechanical polishing. Over a bromine concentration of 0.5 to 3.5 volume percent, the etch rates varied linearly with bromine concentration, were independent of substrate orientation, and, within experimental uncertainties, were identical to those for the etching of CdTe. The etched samples were used as substrates for the organometallic vapor phase epitaxy (OMVPE) growth of CdTe in an impinging jet reactor. The bromine concentration used in etching did not affect the growth rate or the morphology of the deposited CdTe films, but a higher defect density was found for the film grown on a substrate with the orange-peel structure.
Improvement in the Activation Efficiency of Implanted Si in GaAs using Oxygen Plasma Pretreatment
Authors: Cho Jaeshin , Pawlowicz Leszek M. , Saha Naresh C. 
Published: March 2011

ABSTRACTWe have investigated the effect of GaAs surface conditions prior to plasma enhanced chemical vapor deposition of a silicon nitride cap on the activation efficiency of implanted Si in GaAs. The oxygen plasma treatment improved the activation efficiency of implanted Si by ∼35% over (1:10) NH4OH:H2O treatment. X-ray photoelectron spectroscopy (XPS) analysis of the oxygen plasma treated GaAs surface indicated the formation of ∼25Å thick oxide layer consisting of Ga2O3, As2O3, As2O5 and elemental As. During the activation anneal, the arsenic-containing oxides react with the GaAs substrate to form Ga2O3 and elemental As. The presence of excess As between the GaAs and the nitride cap film increases the probability that the implanted Si incorporates in the Ga sites over the As sites, and thereby improves the activation efficiency. This surface-related mechanism suggests that the variation in activation efficiency is mostly attributed to variation in surface conditions, and may explain the wide variety of reported values of activation efficiency.
Vapor Phase Cleaning of Silicon Wafers
Authors: Deal Bruce E. , Helms C. Robert 
Published: March 2011

ABSTRACTVapor phase cleaning of silicon wafers is reviewed. Particular emphasis is placed on oxide etching and removal, including the mechanisms involved in vapor HF etching of silicon oxides. Other items discussed include native oxide formation, impurity removal, and device applications. Future directions involving other chemistries and integrated processing are summarized.
The Effect of Dopant Concentration on the Native Oxide Growth on Silicon Wafer Surface
Authors: Ishimaru Y. , Yoshiki M. , Hatanaka T. 
Published: March 2011

ABSTRACTThe effects of dopant type and dopant concentration on the native oxide growth in air on the silicon surface were investigated. The oxide thickness was measured by X-ray photoelectron spectrometry (XPS). The oxide was thicker on n-type Si than on p-type Si in early oxidation. The oxide increased linearly with the dopant concentration. This enhancement of oxidation was assumed to be caused by vacancies near the surface in the silicon bulk.
Porous Amorphous Si Formation by the Etching of Single Crystal Si Substrates
Authors: George T. , Vasquez R. P. , Kim S. S. , Fathauer R.W. , Pike W. T. 
Published: March 2011

ABSTRACTThe nature of light-emitting porous Si layers produced by non-anodic stain etching of p-type (100) Si substrates is studied. The layers were characterized by transmission electron microscopy as being amorphous in nature. X-ray photoelectron spectroscopy and electron spin resonance measurements show these layers to be composed mainly of a-Si. The formation mechanism of the a-Si is explored using by stain etching SiGe ‘marker’ layers within epitaxially grown Si films and by high temperature annealing. These experiments provide strong evidence for a spontaneous crystalline-amorphous phase transformation during the etching process.
Si MBE on H-Passivated Si(100)
Authors: Eaglesham D.J. , Unterwald F.C. , Luftman H. 
Published: March 2011

ABSTRACTThe use of H-passivation as an initial surface for Si MBE or CVD is becoming more widespread. The H-terminated Si(100) surface is prepared using the spin-etch, vapour-cleaning with HF, or an HF dip, as the final pre-clean before sample loading. The hydrogen is then desorbed in-situ prior to deposition, typically at ≈650 °C. We have shown that deposition directly onto these surfaces leads to epitaxy at substantially lower temperatures (≈350°C). In order to understand how epitaxy occurs far below the hydrogen desorption temperature we have investigated growth on clean Si(100) during deliberate dosing with deuterium in this temperature regime. Since the final coverage observed in SIMS is always far lower than the total dose, we conclude that deposition of Si induces desorption of H, as opposed to simple H segregation.
Photoemission Study of the Si, Ge Epitaxial Growth Process Using Surfactants
Authors: Yang Xiaoyu , Cao Renyu , Terry Jeff , Pianetia Piero 
Published: March 2011

ABSTRACTHeteroepitaxial growth of Ge on Si(100) and Si on Ge(100) surfaces with Sb as a surfactant has been investigated by in situ high resolution photoemission and low energy electron diffraction (LEED). Our results show that an ordered monolayer of Sb atoms saturate the surface dangling bonds and consequently lower the surface free energy. Deposition of Ge or Si on the Sb/Si(100) or Sb/Ge(100) surfaces either at room temperature, followed by mild annealing or deposition at elevated temperature, result in an epitaxial layer of Ge or Si on the substrate, respectively. We provide clear experimental evidence that the deposited Ge or Si atoms changes position with the surface Sb atoms in this process. Ge or Si atoms occupy the epitaxial sites previously occupied by the Sb atoms. The Sb atoms in turn segregate to the surface and form a new ordered layer. The Bi-assisted growth process is also discussed.
Optimization of SI-Wafer Cleaning and the use of Buffer-Layers for Epitaxial Growth of Sige-Layers by VLPCVD at T = 650 C
Authors: Caymax Matty R. , Poortmans J. , Ammel A. Van , Vandervorst W. , Vanhellemont J. , Nijs J. 
Published: March 2011

ABSTRACTFor low-temperature epi-growth in UHV-CVD-systems, the pre-epi, ex-situ cleaning of Si-wafers is known to be very critical. Various ways of etching the chemical oxide-layer after RCA-cleaning have been analysed by SIMS-measurements of the interfacial C, 0 and Bcontamination. Layer growth was performed at 650 C under a flow of 20 sccm of silane at 0.26 Pa. The best results (C and 0 below 2 % of a monolayer, and no detectable amounts of B) were obtained with “dry” etch-procedures, i.e. in which no water-rinse was applied after a normal 2 % HF-dip, or where 1F-vapour was used instead. Growth of Si1-xGex-layers with x < 0.1 succeeds quite well on such prepared substrates; for x between 0.1 and 0.25, we have found the use of a thin, pure Si-buffer layer (150 Å) to be indispensable. For x > 0.25, the growing layer can become quite rough, although this varies in time.
The Dependence of ETCH Pit Density on the Interfacial Oxygen Levels in Thin Silicon Layers Grown by Ultra High Vacuum Chemical Vapor Deposition
Authors: Tejwani Manu J. , Ronsheim Paul A. 
Published: March 2011

ABSTRACTFor low temperature silicon epitaxy it is not only important to have an oxygen free environment during growth but also an initial silicon surface free of trace concentrations of oxygen, carbon and other impurities. Variations in the pre-clean process (using the standard ex-situ aqueous hydrofluoric acid dip) used for ultra high vacuum chemical vapor depostion (UHVCVD) of silicon, result in interfacial oxygen levels ranging from 2 × 1012atoms/cm2 to 1014atoms/cm2 as measured by secondary ion ion mass spectroscopy (SIMS). Using a dilute Schimmel etch we have delineated the dislocations in the thin silicon epitaxial layers grown by UHVCVD. Correlation of the etch pit density to the interfacial oxygen levels suggests a power law dependence. Plausibility arguments are presented to explain this power law dependence.
A Complementary Wafer Cleaning and Growth Process for Low Temperature, Defect Free, Selective Silicon Epitaxy
Authors: Fitch Jon T. , Denning Dean J. 
Published: March 2011

ABSTRACTLow temperature (<850°C) defect free selective silicon epitaxy has been achieved with a conventional barrel type reactor (base pressure -10−4 Torr) using complementary cleaning and growth processes: a wet multi-step oxidizing clean, and a novel non-steady state CVD growth process. With this combination of cleaning and growth processes, it is shown that the need for a high temperature (950-1000°C) insitu native oxide removal step, which may be incompatible with advanced VLSI process integration, is eliminated.
Novel Doping Process for Ultra-Shallow Junction: Rapid Vapor-Phase Direct Doping (RVD)
Authors: Kiyota Yukihiro , Onai Takahiro , Nakamura Tohru , Inada Taroh , Kuranouchi Atsushi , Hirano Yasuaki 
Published: March 2011

ABSTRACTCharacteristics are shown for shallow boron-doped layers formed by a new doping method called Rapid Vapor-phase direct Doping (RVD) which is suitable for making shallow junctions of less than 50 nm. In this method, boron atoms are doped into Si from the vaporphase after the native oxide is removed in hydrogen. From the results obtained for time dependence of doping characteristics, it was found that the surface boron concentration increases almost proportionally to the doping time. This result means that the surface boron concentration is determined by the amount of supplied boron atoms. It is a unique characteristic of this method and a reason why shallow junctions can be fonrned. This method was applied to the base region of a bipolar transistor and produced a normal DC characteristics.
Antimony as A Passivant of Si(111) in the Si(111) (√3×√3)-Sb System
Authors: Hughes A. , Shen T-H. , Matthai C.C. 
Published: March 2011

ABSTRACTThe electronic density of states (DOS) for the Si(111) (√3×√3)-Sb system has been calculated using the tight binding method in the Extended Hiickel Approximation. We find that there is a gap of about 0.8eV between the valence band maximum (VBM) and a surface state. This is in contrast with the case of the unreconstructed (lxl) surface where the Fermi level lies at the surface state.
Surface Cleaning Prior to Formation of Si/SiO2 Interfaces by Remote Plasma-Enhanced Chemical Vapor Deposition (RPECVD)
Authors: Lamb H. H. , Kalem S. , Bedge S. , Yasuda T. , Ma Y. , Lucovsky G. 
Published: March 2011

ABSTRACTEx situ UV/O2 cleaning prior to SiO2 deposition by RPECVD results in an SiO2/Si interface with mid-gap Dit values 2-5 times higher than interfaces formed by in situ exposure of HF-etched wafers to plasma-generated atomic O. In situ exposures to plasma-generated atomic H and atomic O are each effective at removing carbon contamination acquired by the UV/O2 cleaned wafers during transfer and introduction to the RPECVD chamber. However, in situ exposure of the photochemical oxide layer to atomic O results in higher mid-gap Dit values, and in situ exposure to atomic H results in creation of dangling bond defects (Pb centers).