bluuebunny/crossref_metadata_2025_split huggingface dataset:
H Out-Diffusion and Device Performance in n-i-p Solar Cells Utilizing High Temperature Hot Wire a-Si:H i-Layers
Authors: Mahan A. H. , Reedy R. C. , Iwaniczko E. , Wang Q. , Nelson B. P. , Xu Y. , Gallagher A. C. , Branz H. M. , Crandall R. S. , Yang J. , Guha S. 
Published: April 2011

ABSTRACTHydrogen out-diffusion from the n/i interface region plays a major role in controlling the fill factor (FF) and resultant efficiency of n-i-p a-Si:H devices, with the i-layer deposited at high substrate temperatures by the hot wire technique. Modeling calculations show that a thin, highly defective layer at this interface, perhaps caused by significant H out-diffusion and incomplete lattice reconstruction, results in sharply lower device FF's due to the large voltage dropped across this defective layer. One approach to this problem is to introduce trace dopant tailing to ‘compensate’ these defects, but the resultant cells exhibit a poor red response. A second approach involves the addition of buffer layers designed to retard this out-diffusion. We find that an increased H content, either in the n-layer or a thin intrinsic low temperature buffer layer, does not significantly retard this out-diffusion, as observed by secondary ion mass spectrometry (SIMS) H profiles on devices. All these devices have a defect-rich i-layer region near the n/i interface and a poor device efficiency. However, if this low temperature buffer layer is thick enough, the outdiffusion is minimized, yielding nearly flat H profiles and a much improved device performance. We discuss this behavior in the context of the H chemical potentials and H diffusion coefficients in the high temperature, buffer, n-, and stainless steel (SS) substrate layers. The chemical potential differences between the layers control the direction of the H flow and the respective diffusion coefficients, which depend upon many factors such as the local electronic Fermi energy and the extent of the H depletion, determine the rate. Finally, we report a 9.8% initial active area device, fabricated at 16Å/s, using the insights obtained in this study.
Material Aspects of A-Sin:H Based 2D Direct X-Ray Sensor Array
Authors: Popov I. , Doorselaer G. Van , Calster A. Van , Smet H. De , Boesman E. , Callens F. 
Published: April 2011

ABSTRACTThe possibility of creating an 2D X-ray sensor array on the base of a-SiN:H thin films without switching elements and an X-ray conversion layer is presented in this report. The behavior of a-SiN:H Thin-Film Diode under X-ray irradiation, its limitations, and ways of increasing long-term stability and sensitivity of the sensor are discussed.
Process Integration of A-Si:H Schottky Diode and thin Film Transistor for Low-Energy X-Ray Imaging Applications
Authors: Park B. , Murthy R.V.R. , Sazonov A. , Nathan A. , Chamberlain S.G. 
Published: April 2011

ABSTRACTIn this paper, we discuss the various design and fabrication issues related to the process integration of a molybdenum/amorphous silicon (Mo/a-Si:H) Schottky diode and a thin film transistor (TFT), for realization of an X-ray pixel intended for large area and low energy imaging applications. Here, the Schottky diode serves as the sensor and the TFT as a switching element for charge readout. Different pixel configurations are fabricated and compared taking into consideration design aspects such as leakage current, process sequence in terms of mask count, fill factor, and mechanical integrity of various layers. Preliminary X-ray response measurements, over the range (40 – 115) kVp, yield a pixel sensitivity of (1–10) million electrons for a readout sampling period of 16·7 ms.
Carbon Rich a-Si1-xCx:H Films: An Investigation On Radiative Recombination Properties
Authors: Giorgis F. , Giuliani F. , Pirri C.F. , Mandracci P. , Rava P. , Reitano R. , Calcagno L. , Musumeci P. 
Published: April 2011

ABSTRACTAmorphous silicon-carbon a-Sil-xCx:H films with x in the range 0.3-1 have been deposited by PECVD of SiH4+CH4 and SiH4+C2H2 gas mixtures. Photoluminescence characterizations have been performed, together with optical measurements. The dependence of radiative recombination properties as a function of x and as a function of damage introduced by H+-ion irradiation has been presented and correlated with the changes in the absorption spectra.
Photo and Electroluminescence of a-Si:Er:H
Authors: Tessler Leandro R. , Iñiguez Ana Carola 
Published: April 2011

ABSTRACTTrivalent erbium (Er3+) presents a characteristic intra 4f optical transition 4I13/2 → 4I15/2 at 1.54 μm when incorporated in several solid hosts. Hydrogenated amorphous silicon (a-Si:H) is a good candidate as a host for applications in optical communications and photonic integration. We have studied Er3+ photo and electroluminescence in a-Si:H prepared by co-sputtering from a silicon target partially covered with metallic erbium chunks. Since the presence of oxygen impurities enhances the luminescence intensity, we studied the influence of oxygen added to the sputtering gas on the material properties. We found that oxygen reduces the erbium incorporation into the films. We obtained samples presenting 1.54 μm photoluminescence as deposited for a wide range of erbium concentrations. Maximum room-temperature photoluminescence efficiency is obtained for samples that contain ∼ 1% [O]/[Si] concentrations. The temperature quenching is small, mainly due to the temperature dependence of the luminescence lifetime.Room temperature electroluminescence at 1.54 νm was observed in reverse biased Si/a-Si:Er:O:H/Al structures.
Annealing Effect on the Activation of 1.54 [νm Emission from Erbium in a-Si:H Matrix Prepared by DC Magnetron Sputtering
Authors: Andreev A.A. , Golubev V.G. , Medvedev A.V. , Pevtsov A.B. , Voronkov V.B. 
Published: April 2011

ABSTRACTCumulative thermal annealing (TA) changes the photoluminescence (PL) intensity in erbium-doped a-Si:H films prepared using DC magnetron sputtering of a composite Er-Si target at substrate temperature 200°C. The intensity of erbium-related 1.54 νm PL at 77 K is enhanced about 50 times after TA at 300°C for 15 min in nitrogen atmosphere. No erbium-related PL is observed after TA at T≤500°C. The TA process is discussed in terms of a model of partial structural rearrangement in an a-Si(Er):H amorphous network.
Design of Atcd three Color Detector for Color Detection in Transient Regime
Authors: Irrera F. , Palma F. , Lemmi F. , Diotallevi M. 
Published: April 2011

ABSTRACTIn this paper we present the characterization of an ATCD three color detector used in the charge integration regime, as necessary in large area matrices. In particular, we present linearity measurements of mesa insulated devices and characterization of the self-bias process occurring in the transient read-out of stacked structures. A new system architecture is introduced which considers interlaced row charge restore, and separates the charge restore process from the charge sampling process in order to reach self-bias within a short frame time.
Image Sensors in Tfa Technology - Status and Future Trends
Authors: Böhm M. , Blecher F. , Eckhardt A. , Seibel K. , Schneider B. , Sterzel J. , Benthien S. , Keller H. , Lulé T. , Rieve P. , Sommer M. , Uffel B. Van , Librecht F. , Lind R. C. , Humm L. , Efron U. , Roth E. 
Published: April 2011

ABSTRACTImage sensors in TFA (Thin Film on ASIC) technology have been successfully fabricated and tested. This paper provides a survey of TFA research results so far and outlines future perspectives. The properties of different a-Si:H b/w and color thin film detectors are evaluated, including spectral sensitivity, dark current, temperature influence and transient behavior. Furthermore several TFA prototypes and emerging concepts are presented, ranging from a simple one-transistor cell design to a locally autoadaptive sensor.
A Polysilicon Tft Parameter Extractor
Authors: Lui O.K.B. , Tam S.W.B. , Migliorato P. 
Published: April 2011

ABSTRACTThe achievement of large size displays and the capability of high throughput low temperature laser re-crystallised polysilicon TFTs to provide complex circuitry has opened up new market opportunities, such as the “system on panel” architecture, where the circuitry necessary for the operation of an interactive portable computer is to be fabricated on the display substrate. In the development of polysilicon technology for these applications, device physics and modelling are expected to play a major role as they have done in the case of single crystal silicon. However, polysilicon TFTs present a much higher level of complexity than single crystal devices, due to the presence of grain boundaries and associated defects which drastically affect the electrical properties. For the first time, a polysilicon TFT parameter extractor has been developed based on data from capacitance (C-V) and conductance (I-V) measurements. The method yields the flat band voltage, the front interface state density and the bulk density-of-states (DOS) for the entire range. The method is applied to laser re-crystallised polysilicon TFTs and verified via comparison with 2-D simulation. It is found that this technique allows a much higher degree of accuracy than other methods published so far.
High Conductivity Gate Metallurgy for Tft/Lcd's
Authors: Fryer Peter M. , Colgan E. , Galligan E. , Graham W. , Horton R. , Jenkins L. , John R. , Kuo Y. , Latzko K. , Libsch F. , Lien A. , Nywening R. , Polastre R. , Rothwell M. E. , Wilson J. , Wisnieff R. , Wright S. 
Published: April 2011

ABSTRACTAmorphous silicon based thin film transistor liquid crystal displays (TFT/LCD) have become the dominant technology used for flat panel displays for notebook computers. The need for higher resolution, larger diagonal displays for both notebook and desktop applications is discussed. Calculations have shown that the use of high conductivity gate metal such as aluminum or copper, together with the implementation of improved groundrules, can significantly extend today's technology. Aluminum suffers from problems with hillock formation during PECVD processing, and copper typically has poor adhesion to glass, reaction problems with silicon and other PECVD films, and difficulties in contacting it to other metals. Approaches to solving problems with both materials are presented, and a novel reduced mask process to fabricate high resolution, high aperture ratio 10.5” SXGA (1280×1024) displays is described. The process uses copper gate metallurgy with redundancy, without the need for extra processing steps. The resulting displays have 150 dpi color resolution, an aperture ratio of over 35%, and excellent image quality, making them the first high resolution displays that are suitable for notebook applications.
Computer Simulation for Solar Cell Applications: Understanding and Design
Authors: Zhu Hong , Fonash Stephen J 
Published: April 2011

ABSTRACTComputer device transport simulation can be a very powerful tool for device physics understanding, design, and optimization. This is especially true when it is done with a PC version that can be easily run on the desktop. However, like any powerful tool, computer simulation must be used with care and appreciation. Using our newest version of our AMPS (Analysis of Microelectronic and Photonic Structures) [1,2] transport physics code, AMPS for Windows 95/NT, we discuss using solar cell simulations for increased understanding, for materials evaluation, and for device design and optimization.
Defect Distributions in Doped and Undoped A-SiGe:H Alloys
Authors: Stiebig Helmut , Siebke Frank , Carius Reinhard , Klomfaβ Josef 
Published: April 2011

ABSTRACTIn this work, gap states in doped and undoped a-SiGe:H alloys are examined by numerical simulations of sub-bandgap absorption spectra measured by the constant photocurrent method and photothermal deflection spectroscopy. Deconvolution methods, neglecting the condition of charge neutrality, can be used for a rough estimate of the defect density value but not for ob- taining detailed information on the distribution of gap states in undoped samples. Our numerical analysis uses adapted occupation statistics and takes into account the condition of charge neutrality. Good agreement between measured and simulated PDS and CPM spectra is obtained. For a certain composition, i.e. a certain bandgap, the investigation of doped films yields infor- mation on the density and the position of charged defect states in the bandgap. In addition, the density of neutral defect states can be derived from a comparison of CPM and PDS spectra. The results reveal the coexistence of charged and neutral defects. In doped as well as in undoped films, charged defect states dominate the defect density. In the investigated range of compo- sitions the defect distribution of a-SiGe:H is similar to those found in a-Si:H. The width of the defect distributions does not decrease with decreasing bandgap. No evidence for a different be- havior of Si- and Ge-related defect states can be found in sub-bandgap absorption spectra.
Device Modeling of a-Si:H Alloy Solar Cells: Calibration Procedure for Determination of Model Input Parameters
Authors: Zeman M. , Van Swaaij R.A.C.M.M. , Schroten E. , Vosteen L.L.A. , Metselaar J.W. 
Published: April 2011

ABSTRACTA calibration procedure for determining the model input parameters of standard a-Si:H layers, which comprise a single junction a-Si:H solar cell, is presented. The calibration procedure consists of: i) deposition of the separate layers, ii) measurement of the material properties, iii) fitting the model parameters to match the measured properties, iv) simulation of test devices and comparison with experimental results. The inverse modeling procedure was used to extract values of the most influential model parameters by fitting the simulated material properties to the measured ones. In case of doped layers the extracted values of the characteristic energies of exponentially decaying tail states are much higher than the values reported in literature. Using the extracted values of model parameters a good agreement between the measured and calculated characteristics of a reference solar cell was reached. The presented procedure could not solve directly an important issue concerning a value of the mobility gap in a-Si:H alloys.
The Effect of Ion-Bombardment on the Formation of Voids During Deposition of a-Ge:H
Authors: Origo F. , Hammer P. , Comedi D. , Chambouleyron I. 
Published: April 2011

ABSTRACTThe role of substrate ion bombardment on the structural and H bonding properties of hydrogenated amorphous germanium (a-Ge:H) films was studied by infrared (ir) spectroscopy. A Kaufman type ion source was used to produce an Ar1 beam directed towards a Ge target for a- Ge:H ion beam sputtering deposition in a H2-containing vacuum chamber. A low energy (100 eV) H2++Ar+ beam obtained from an additional ion source was allowed to impinge directly on the substrate during film growth at various beam currents.It was found that substrate bombardment by 100 eV ions favors the formation of voids, as deduced from the increasing contribution of the surface-like Ge-H stretching mode to the ir spectrum with increasing ion current. The void density was reduced below the ir detection limit by totally removing the ion beam on the substrate while keeping all other parameters fixed. For this condition, we observe no or very small surface-like contributions to the ir spectra, irrespective of substrate temperature (25-260°C) or growth rate used. A narrowing of the infrared Ge-H stretching mode peak is observed with increasing deposition temperature, indicating a concomitant tendency towards a more ordered structure.
Hydrogen in a-Si:H Deposited by an Expanding Thermal Plasma: A Temperature, Growth Rate and Isotope Study
Authors: Kessels W.M.M. , Sanden M.C.M. Van De , Severens R.J. , Ijzendoorn L.J. Van , Schram D.C. 
Published: April 2011

ABSTRACTThe hydrogen and silicon density of a-Si:H-films deposited by an expanding thermal plasma have been investigated for a wide range of substrate temperatures and growth rates by infrared absorption spectroscopy in combination with elastic recoil detection and Rutherford backscattering. The study reveals that, despite the increasing atomic hydrogen interaction and high substrate temperatures, the a-Si:H remains purely amorphous at low growth rates as concluded from Raman spectroscopy. Additionally, the infrared spectroscopy proportionality constants of the silicon-hydrogen and silicon-deuterium bondings have been recalibrated.
Large Area Deposition of Amorphous and Microcrystalline Silicon by Very High Frequency Plasma
Authors: Sansonnens L. , Howling A. A. , Hollenstein Ch. 
Published: April 2011

ABSTRACTTwo aspects of VHF plasma deposition in a large area reactor are investigated: 1) Experiments and model show that voltage inhomogeneities become serious at high frequency but can be reduced by suitable RF connection configuration. These voltage inhomogeneities are the main factor limiting the excitation frequency in order to satisfy film thickness uniformity requirements; 2) the effect of the frequency on the plasma properties has been studied between 13.56 MiHz and 70 MHz. The results show that an increase of the electron density with the frequency leads to a more efficient dissociation of silane. This increase of the gas phase reactivity of the plasma is largely responsible for the higher deposition rates observed athigh frequency.The choice of the excitation frequency for a given application is a compromise between the gain of higher deposition rate and the frequency limit imposed by homogeneity requirements.
Dust Particle Diagnostics in Rf Plasma Deposition of Silicon and Silicon Oxide Films (Invited)
Authors: Hollenstein Ch. , Howling A. A. , Courteille C. , Dorier J.-L. , Sansonnens L. , Magni D. , Müller H. 
Published: April 2011

ABSTRACTParticle contamination formed in reactive plasmas imposes an upper limit on the rate for particle-free deposition. Conversely, these plasmas could be exploited to produce nanometric clusters and particles for various applications. Infrared absorption spectroscopy has been applied to analyse the chemical composition of suspended particles. Mass spectrometry was also used to investigate cluster formation in these deposition plasmas. In pure silane plasmas, a random model reproduces the measured mass spectra, whereas the rich plasma chemistry in silane/oxygen mixtures shows a remarkable tendency to produce silasesquioxane anions.
Metastability of Phosphorus- or Boron Doped a-Si:H Films
Authors: St'ahel P. , Cabarrocas P. Roca i , Sladek P. , Theye M.L. 
Published: April 2011

ABSTRACTThe effects of light-soaking on either phosphorus- or boron-doped a-Si:H films were studied as functions of the doping level and the temperature. In the case of boron-doped films, the most important effect is the improvement of the conductivity during light-soaking, which is related to the activation of boron. On the contrary, phosphorus-doped films present a remarkable stability, although lightly phosphorus-doped ones show a decrease of their conductivity by five orders of magnitude when light-soaking is performed below 40 °C. This effect is attributed to the formation of P-H complexes which are stable at low temperature only. Our results suggest that in both types of doped a-Si:H films the creation of metastable defects is a second order effect with respect to the activation or passivation of dopants, which results from their interaction with hydrogen.
The Role of Charged Defects In Current Transport Through Hydrogenated Amorphous Silicon Alloys
Authors: Lau S.P. , Shannon J.M. , Sealy B.J. , Marshall J.M. 
Published: April 2011

ABSTRACTCurrent transport in metal-semiconductor-metal structures based on amorphous silicon alloys has been studied in relation to the density of dangling bond state defects. The density of defects was changed by varying alloy composition or by current stressing. We show that the change of current-voltage characteristics and activation energy with defect density and the onset of Poole-Frenkel conduction with composition require charged defects. It is found that there are more charged defects in amorphous silicon nitride (a-Si1−xNx:H) than in amorphous silicon carbide (a-Si1−xCx:H). In addition, an excess of negatively charged dangling bond defects compared to positively charged dangling bond defects is observed in a-Si1−xNx:H films. This is attributed to the presence of N4+ act as the donor states in silicon nitride. We find that the density of charged dangling bond defects can be higher than 1019cm−3.
Light-Induced Change of Si-H Bond Absorption in Hydrogenated Amorphous Silicon
Authors: Yue Guozhen , Chen Liangfan , Wang Qi , Iwaniczko Eugene , Kong Guanglin , Baugh Jonathan , Wu Yue , Han Daxing 
Published: April 2011

ABSTRACTDevice-quality a-Si:H films were prepared by glow discharge CVD with pure or H-diluted silane as well as by hot-wire CVD. The hydrogen content was varied from ∼2 to 15 at. %. The Si-H bond absorption and its light-soaking-induced changes were studied by IR and differential IR absorption spectroscopes. The results indicate that the more stable sample exhibits an increase of the absorption at wave number ∼2000 cm−1, and the less stable one exhibits a decrease at ∼2040 cm−1and an increase at ∼1880 cm−1.
Hydrogen Collision Model of The Staebler-Wronski Effect: Microscopics and Kinetics
Authors: Branz Howard M. 
Published: April 2011

ABSTRACTA new microscopic and kinetic model of light-induced metastability in hydrogenated amorphous silicon (a-Si:H) is described. Recombination and trapping of photoinduced carriers excite hydrogen from deep Si-H bonds into a mobile configuration, leaving a dangling bond (DB) defect at the site of excitation. Normally, mobile H are recaptured at DB defects and no metastability or net DB production results. However, when two mobile H collide, they form a metastable two-hydrogen complex and leave two spatially-uncorrelated Staebler-Wronski DBs. Thermal and light-induced annealing occur when mobile H are excited from the metastable two-H complex; they diffuse and are recaptured to DBs. The microscopic model is entirely compatible with electron-spin-resonance results showing neither DB-DB nor DB-H spatial correlation of the light-induced DBs. The model leads to new differential equations describing the evolution of the mobile H and DB densities. These equation equations explain the observed room-temperature Ndb∼G2/3t1/3 dependence of DB creation upon the electron-hole pair creation rate (G) and time. The model also accounts for both t1/3-kinetics at 4.2K and t1/2-kinetics under laser-pulse soaking. Neither of these results can be explained within the prevailing electron-hole pair recombination model.
Pulsed Esr Studies on Microcrystalline Silicon
Authors: Malten C. , Finger F. , Müller J. , Yamasaki S. 
Published: April 2011

ABSTRACTTwo-pulse-echo field-sweep spectra of boron-doped samples show in addition to dangling bonds (DB) a very broad feature of approximately 500 G width. This feature is the sum of several lines whose relative intensities change with doping and temperature. The total intensity increases with doping. The spin-lattice relaxation time TI of the resonance at g=1.998 referred to as conduction electrons (CE) has been studied for undoped and P-doped microcrystalline silicon. The discrepancy between T1 values previously reported has been resolved and the values for CE are at least two orders of magnitude smaller than those of the DB. In undoped samples cross-relaxation between the CE and DB spin systems might explain the similar T1 values obtained for CE and DB in inversion recovery measurements.