bluuebunny/crossref_metadata_2025_split huggingface dataset:
Uniformity and Quality of Monocrystalline Silicon Passivation by Thin Intrinsic Amorphous Silicon in a New Generation Plasma-enhanced Chemical Vapor Deposition Reactor
Authors: Strahm Benjamin , Andrault Yoann , Bäetzner Derk , Lachenal Damien , Guérin Chloé , Kobas Manuela , Mai Joachim , Mendes Bruno , Schulze Thomas , Wahli Guillaume , Buechel Arthur 
Published: August 2010

AbstractThis work reports the first results of a new generation plasma-enhanced chemical vapor deposition (PECVD) reactor manufactured by Roth and Rau. This large area parallel plate reactor has been especially designed for the manufacturing of silicon heterojunction solar cells which are made of very thin amorphous silicon films over monocrystalline silicon substrates. Layer thickness uniformity below ± 3 % is reported for both intrinsic and doped layer over a 400 × 400 mm2 area. Moreover, it is shown that the passivation quality is excellent with life-times up to 4.15 ms on n-type FZ silicon substrates. A ± 0.6 % uniformity in open circuit voltage (mean value of 701.4 mV) is achieved over 32 devices having a 4 cm2 area and an average conversion efficiency of 19.5 %.
Microstructure Effects in Amorphous and Microcrystalline Ge:H Films
Authors: Beyer Wolfhard , Einsele Florian , Kondo Michio , Matsui Takuya , Pennartz Frank 
Published: August 2010

AbstractThe characterization of void-related microstructure in amorphous and microcrystalline Ge:H films is reported. Various methods are applied including effusion measurements of hydrogen and of implanted helium and neon, measurements of the infrared absorption of C-H bonds due to in-diffusion of contaminants and of the stretching modes of bonded hydrogen. Several microstructure effects like interconnected voids and isolated voids and a quite different material homogeneity are detected and are found to depend on the preparation conditions. Amorphous Ge:H can be prepared with a (largely) homogeneous structure while microcrystalline Ge:H tends to consist of compact grains surrounded by more or less open voids. Enhanced substrate temperatures (Ts ≈ 250°C) favour the growth of more compact material.
Effects of Grain Boundaries on Performance of Hydrogenated Nanocrystalline Silicon Solar Cells
Authors: Su Tining , Bobela David , Xu Xixiang , Ehlert Scott , Beglau Dave , Yue Guozhen , Yan Baojie , Banerjee Arindam , Yang Jeff , Guha Subhendu 
Published: August 2010

AbstractWe investigate the effect of hydrogenation of grain boundaries on the performance of solar cells for hydrogenated nanocrystalline silicon (nc-Si:H) thin films. Using hydrogen effusion, we found that the amplitude of the lower temperature peak in the H-effusion spectra is strongly correlated to the open-circuit voltage in solar cells. This is attributed to the hydrogenation of grain boundaries in the nc-Si:H films.
Material Properties of a-SiGe:H Solar Cells as a Function of Growth Rate
Authors: Hugger Peter , Lee JinWoo , Cohen J. David , Yue Guozhen , Xu Xixiang , Yan Baojie , Yang Jeff , Guha Subhendu 
Published: August 2010

AbstractWe have examined a series of a Si,Ge:H alloy devices deposited using both RF and VHF glow discharge in two configurations: SS/n+/i (a-SiGe:H)/p+/ITO nip devices and SS/n+/i (a-SiGe:H)/Pd Schottky contact devices, over a range of deposition rates. We employed drive-level capacitance profiling (DLCP), modulated photocurrent (MPC), and transient junction photo-current (TPI) measurement methods to characterize the electronic properties in these materials. The DLCP profiles indicated quite low defect densities (mid 1015 cm-3. to low 1016 cm-3 depending on the Ge alloy fraction) for the low rate RF (∼1Å/s) deposited a-SiGe:H materials. In contrast to the RF process, the VHF deposited a-SiGe:H materials did not exhibit nearly as rapid an increase of defect density with the deposition rate, remaining well below 1017 cm-3. up to rates as high as 10Å/s. Simple examination of the TPI spectra on theses devices allowed us to determine valence band-tail widths.. Modulated photocurrent (MPC) obtained for several of these a-SiGe:H devices allowed us to deduce the conduction band-tail widths. In general, the a-Si,Ge:H materials exhibiting narrower valence band-tail widths and lower defect densities correlated with the best device performance.
Improving Performance of Amorphous Silicon Solar Cells Using Tungsten Oxide as a Novel Buffer Layer between the SnO2/p-a-SiC Interface
Authors: Fang Liang , Baik Seung Jae , Lim Koseng Su , Yoo Seung Hyup , Seo Myung Soo , Kang Sang Jung 
Published: August 2010

AbstractA thermally evaporated p-type amorphous tungsten oxide (p-a-WO3) film was introduced as a novel buffer layer between SnO2 and p-type amorphous silicon carbide (p-a-SiC) of pin-type amorphous silicon (a-Si) based solar cells. By using this film, a-Si solar cells with a p-a-WO3/p-a-SiC double p-layer structure were fabricated and the cell photovoltaic characteristics were investigated as a function of p-a-WO3 layer thickness. By inserting a 2 nm-thick p-a-WO3 layer between SnO2 and a 6 nm-thick p-a-SiC layer, the short circuit current density increased from 9.73 to 10.57 mA/cm2, and the conversion efficiency was enhanced from 5.17 % to 5.98 %.
Preparation of Narrow-gap a-Si:H Solar Cells by VHF-PECVD Technique
Authors: Kim Do Yun , Yunaz Ihsanul Afdi , Kasashima Shunsuke , Miyajima Shinsuke , Konagai Makoto 
Published: August 2010

AbstractOptical, electrical and structural properties of silicon films depending on hydrogen flow rate (RH), substrate temperature (TS), and deposition pressure (PD) were investigated. By decreasing RH and increasing TS and PD, the optical band gap (Eopt) of silicon thin films drastically declined from 1.8 to 1.63 eV without a big deterioration in electrical properties. We employed all the investigated Si thin films for p-i-n structured solar cells as absorbers with i-layer thickness of 300 nm. From the measurement of solar cell performances, it was clearly observed that spectral response in long wavelength was enhanced as Eopt of absorber layers decreased. Using the solar cell whose Eopt of i-layer was 1.65 eV, the highest QE at long wavelength with the short circuit current density (Jsc) of 16.34 mA/cm2 was achieved, and open circuit voltage (Voc), fill factor (FF), and conversion efficiency (η) were 0.66 V, 0.57, and 6.13%, respectively.
A Highly Sensitive Integrated a-Si:H Fluorescence Detector for Microfluidic Devices
Authors: Kamei Toshihiro , Shikanai Amane 
Published: August 2010

AbstractMost of micromachined and/or integrated fluorescence detectors suffer from high limit of detection (LOD) compared to conventional optical system that consists of discrete optical components, which is mainly due to higher laser light scattering of integrated optics rather than detector sensitivity. In this work, we have reduced background (BG) photocurrent of an integrated hydrogenated amorphous Si (a-Si:H) fluorescence detector due to laser light scattering by nearly one order magnitude, significantly improving a LOD. The detection platform comprises a microlens and the annular fluorescence detector where a thick SiO2/Ta2O5 multilayer optical interference filter (>6 μm) is monolithically integrated on an a-Si:H pin photodiode. With a microfluidic capillary electrophoresis (CE) device mounted on the platform, the system is demonstrated to separate DNA restriction fragment digests (LOD: 58 pg/μL) as well as 2 nM of fluorescein-labeled oligomer (LOD: 240 pM) with high speed, high sensitivity and high separation efficiency. The integrated a-Si:H fluorescence detector exhibits high sensitivity for practical fluorescent labeling dyes as well as feasibility of monolithic integration with a laser diode, making it ideal for application to point-of-care microfluidic biochemical analysis.
Reviewing Photo-sensing Devices Using a-SiC Based Materials
Authors: Vieira Manuela , Fernandes Miguel , Louro Paula , Fantoni Alessandro , Vieira M. A. , Costa João , Barata Manuel 
Published: August 2010

AbstractIn this paper a double pi'n/pin a-SiC:H voltage and optical bias controlled device is presented and it behavior as image and color sensor, optical amplifier and multiplex/demultiplex device discussed. The sensing element structure (single or tandem) and the light source properties (wavelength, intensity and frequency) are correlated with the sensor output characteristics (light-to-dark sensivity, resolution, linearity, bit rate and S/N ratio). Depending on the application, different readout techniques are used. When a low power monochromatic scanner readout the generated carriers the transducer recognize a color pattern projected on it acting as a color and image sensor. Scan speeds up to 104 lines per second are achieved without degradation in the resolution. If the photocurrent generated by different monochromatic pulsed channels is readout directly, the information is multiplexed or demultiplexed. It is possible to decode the information from three simultaneous color channels without bit errors at bit rates per channel higher than 4000bps. Finally, when triggered by appropriated light, it can amplify or suppress the generated photocurrent working as an optical amplifier. An electrical model is presented to support the sensing methodologies. Experimental and simulated results show that the tandem devices act as charge transfer systems. They filter, store, amplify and transport the photogenerated carriers, keeping its memory (color, intensity and frequency) without adding any optical pre-amplifier or optical filter as in the standard p-i-n cells.
A New Perspective on an Old Problem: The Staebler-Wronski Effect
Authors: Fritzsche Hellmut 
Published: August 2010

AbstractPhoto-induced structural changes and defect creation are common phenomena in a large variety of polymeric and non-crystalline semiconductors. The photo-induced degradation of a-Si:H and its alloys, discovered by Staebler and Wronski in 1977, belongs to a special category with quite unique features, which so far has resisted an explanation. Part of the problem is that the near 4-fold coordinated network does not naturally form an amorphous material. It is over-constrained and forms a stress relief void structure. While reviewing the experimental evidence it will be argued that some of our commonly held views regarding the underlying mechanisms of the Staebler-Wronski effect (SWE) may have to be abandoned. First, the internal void surfaces seem to be the principal locations of the photo-structural changes. Second, non-radiative bimolecular recombinations of photo carriers do not seem to be the driving force of defect creation at helium temperatures. Alternative pathways for the photo-induced processes will be suggested.
A Thermodynamic Model for the Laser Fluence Ablation Threshold of PECVD SiO2 on Thin a-Si:H Films Deposited on Crystalline Silicon
Authors: Mangersnes Krister , Foss Sean Erik 
Published: August 2010

AbstractWe have developed a thermodynamic model that predicts the heat distribution in a stack of PECVD SiO2 and a-Si:H on crystalline Si after laser irradiation. The model is based on solving the total enthalpy heat equation with a finite difference scheme. The laser used in the model is a frequency doubled Nd:YVO4 green laser with pulse duration in the nanosecond range. The modeling was done with the aim of getting a better understanding of our newly developed laser ablation process for making local contacts on back-junction silicon solar cells. Lasers with pulse duration within the nanosecond range are usually believed to induce too much thermal damage into the underlying silicon to make them suitable for high efficiency solar cells. In our case, insertion of a thin layer of a-Si:H between the SiO2 and the Si absorbs much of the laser irradiation both optically and thermally. This makes it possible to form local contacts to Si in a damage-free way. In addition, the residual a-Si:H serves as an excellent surface passivation layer for the Si substrate. We have also developed a simple static model to determine the onset of SiO2 ablation on a-Si:H layers of varying thickness. The models, both the static and the dynamic, are in good agreement with experimental data.
Low Temperature Dopant Activation Using Variable Frequency Microwave Annealing
Authors: Alford Terry L. , Sivaramakrishnan Karthik , Indluru Anil , Ahmad Iftikhar , Hubbard Bob , David Theodore 
Published: August 2010

AbstractVariable frequency microwaves (VFM) and rapid thermal annealing (RTA) were used to activate ion implanted dopants and re-grow implant-damaged silicon. Four-point-probe measurements were used to determine the extent of dopant activation and revealed comparable resistivities for 30 seconds of RTA annealing at 900 °C and 6-9 minutes of VFM annealing at 540 °C. Ion channeling analysis spectra revealed that microwave heating removes the Si damage that results from arsenic ion implantation to an extent comparable to RTA. Cross-section transmission electron microscopy demonstrates that the silicon lattice regains nearly all of its crystallinity after microwave processing of arsenic implanted silicon. Secondary ion mass spectroscopy reveals limited diffusion of dopants in VFM processed samples when compared to rapid thermal annealing. Our results establish that VFM is an effective means of low-temperature dopant activation in ion-implanted Si.
Deep-Level Defects in Electron Irradiated 6H-SiC
Authors: Kozubal Michal Sebastian , Kaminski Pawel , Warchol Stanislaw , Racka-Dzietko Katarzyna , Grasza Krzysztof , Tymicki Emil 
Published: August 2010

AbstractAn effect of electron irradiation on the concentrations of deep-level centers in C-rich and Si-rich 6H-SiC wafers is investigated. In the former material, the main deep-level centers with activation energies of Ec-0.50, Ec-0.64 and Ec-0.67 eV are found to be related to dicarbon interstitials and CiNC complexes located in hexagonal and quasi-cubic lattice sites, respectively. In the latter material, the dicarbon interstitials are dominant after the irradiation with 1.5-MeV electrons. At the energy of bombarding electrons equal to 0.3 and 0.7 MeV, the activation energies of the dominant deep-level centers are Ec-0.38 and Ec-0.52 eV, respectively. The first center is related to carbon vacancies and the second to silicon interstitials.
Optimization of Poly-silicon Process for 3C-SiC Based MOS Devices
Authors: Esteve Romain , Schoner Adolf , Reshanov Sergey A. , Zetterling Carl-Mikael 
Published: August 2010

AbstractCubic 3C-SiC is regarded as a perfect material for medium power MOSFETs with blocking voltages of around 1500V and current handling of 100A and more. One of the main issues to realize such power MOSFETs is the improvement of the MOS gate to ensure low on-state resistance operation.The benefits of the implementation of an advanced oxidation process combining PECVD SiO2 deposition and short post-oxidation steps in wet oxygen has been previously demonstrated [1]. The concentrations of fixed and mobile charges in the oxide and at the SiO2/SiC interface were significantly reduced. But the optimization of the gate material is still an issue.The experiences from silicon technology point in the direction of using a poly-Si gate for MOS controlled devices. Significant improvements in terms of gate oxide reliability could be achieved by applying a poly-Si gate. But the usage of hydrogen for passivation of defects in oxides grown on 3C-SiC gives restrictions to the poly-Si deposition and activation process conditions. A reduced thermal budget is required to preserve the high electrical properties of the oxide.We investigated the electrical properties of MOS structures prepared with poly-Si gates. The poly-Si layer was deposited by the LPCVD technique mixing Si2H6 and PH3 at 380°C. The poly-Si activation has been carried out with five different methods. The influence of the following two main parameters has been considered: the process duration (thermal annealing or rapid thermal annealing) and the gas atmosphere (argon, dry or wet oxygen).MOS capacitors were fabricated on the oxidized free-standing n-type 3C-SiC (001) wafers with 5μm low nitrogen doped (5×1015 cm-3) epitaxial layers. The MOS capacitors were characterized on the wafer level (about 200 MOS structures per wafer) by capacitance-conductance-voltage (C-G-V) measurements using a HP4284A LCR meter in the frequency range of 100 Hz to 1 MHz. The measurements were performed at room temperature in a light-tight and electrically shielded environment. The interface trap densities Dit were extracted by the conductance method. To assess the oxide reliability, time-zero dielectric breakdown (TZDB) measurements were conducted on the fabricated MOS structures.The optimized poly-Si activation process based on RTA in argon has minimal thermal budget and preserves the oxide and interface quality. The fabricated MOS structures demonstrate high electrical properties and reliability of the oxide: A small negative flat band voltage shift of -1V and an interface state density Dit of 7.4×1010 eV-1cm-2 at 0.63 eV below the conduction band. The TZDB measurements revealed an average breakdown electric field of 9.4 MV/cm.
Epitaxial Deposition of 3C-SiC on Si Using Unconventional Sputtering of a Hollow Cathode
Authors: Huguenin-Love James L , Soukup Rodney J , Ianno Natale J , Lauer Nole T 
Published: August 2010

AbstractEpitaxial 3C-SiC was grown using an unconventional technique for epitaxial growth. Thin films of 3C-SiC were deposited onto the (111) and (110) faces of Si using pulsed DC sputtering of a high purity, hollow cathode SiC target. The films were studied using x-ray diffraction (XRD), reflection high energy electron diffraction (RHEED), transmission electron microscopy (TEM), and auger electron spectroscopy (AES) techniques. XRD results presented as Bragg diffraction spectra and pole figures, and electron diffraction patterns verify crystal orientation and epitaxy. In addition, AES profiles identify the compositional integrity of the deposited films.
SiC Bipolar Power Transistors - Design and Technology Issues for Ultimate Performance
Authors: Ostling Mikael , Domeij Martin , Zaring Carina , Konstantinov Andreij , Ghandi Reza , Buono Benedetto , Hallen Anders , Zetterling Carl-Mikael 
Published: August 2010

AbstractSilicon carbide (SiC) semiconductor devices for high power are becoming more mature and are now commercially available as discrete devices. Schottky diodes have been on the market since a few years but also bipolar junction transistors (BJTs), JFETs and MOSFETs are now reaching the market. The interest is rapidly growing for these devices in high power and high temperature applications. The BJTs have low conduction losses, fast switching capability, operate in normally-off mode, have high radiation hardness, and can handle high power density.This paper will review the current state of the art in active switching device performance with special emphasis on BJTs. Device performance has been demonstrated over a wide temperature interval. A very important feature in high power switch applications is the low on-resistance of a device. Better material quality and epi processes suppress the amount of basal plane dislocations to avoid stacking fault formation generated during high current injection. This has long been a concern for bipolar SiC devices but several research reports and long term reliability measurements of pn-junctions show that the bipolar degradation problem can be solved by a fine-tuned epitaxial technique. A discussion on surface passivation control is included.Finally, an example of a power switching module is given also demonstrating the excellent paralleling capability of BJTs.
Bandstructure Manipulation of Epitaxial Graphene on SiC(0001) by Molecular Doping and Hydrogen Intercalation
Authors: Starke Ulrich 
Published: August 2010

AbstractGraphene, a monoatomic layer of graphite hosts a two-dimensional electron gas system with large electron mobilities which makes it a prospective candidate for future nanocarbon devices. Grown epitaxially on silicon carbide (SiC) wafers, large area graphene samples appear feasible and integration in existing device technology can be envisioned. A precise control of the number of graphene layers and growth of large homogeneous graphene samples can be achieved. However, as-grown epitaxial graphene on SiC is electron doped due to the influence of the reconstructed interface layer present between graphene and SiC. Covalent bonds between SiC and the first carbon layer grown on top induce a dipole layer which induces charges into the graphene. As a result, the Dirac point energy where the π-bands cross is shifted away from the Fermi energy, so that the ambipolar properties of graphene cannot be exploited. How this effect can be overcome by a precise control and manipulation of the electronic structure of the π-bands is demonstrated by two methods. On the one hand, transfer doping of the epitaxial graphene surfaces with the strong acceptor molecule tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) allows for a fine tuning of the doping level. Charge neutrality can be achieved for mono- and bilayer graphene. On bilayer samples the magnitude of the existing bandgap can be increased up to more than double of its initial value. On the other hand, the impact of the SiC-graphene interface can be completely eliminated by annealing the samples in molecular hydrogen. The hydrogen atoms migrate through the graphene layers, intercalate between the SiC substrate and the interface layer and bind to the Si atoms of the SiC(0001) surface. Thus the interface layer, decoupled from the SiC substrate, is turned into a quasi-free standing graphene monolayer. Similarly, epitaxial monolayer graphene turns into a decoupled bilayer. The intercalation process represents a highly promising route towards epitaxial graphene based nanoelectronics.
Graphene Growth on SiC and Metal Surfaces by Solid Source Carbon Deposition
Authors: Mitchel W. C. , Park J. H. , Smith H. E. , Grazulis L. 
Published: August 2010

AbstractGraphene has been grown by direct deposition of carbon from solid sources on both SiC and Ta films on SiC in an MBE environment. Carbon fluxes were obtained from thermally evaporated C60 and from a heated graphite filament. The graphene films were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. Graphene films on Si-face SiC grown by carbon source MBE (CSMBE) were compared with graphene grown by the standard epitaxial graphene process using SiC thermal decomposition. CSMBE on SiC was found to grow at lower temperatures (1200°C) and to have fewer pits and a more uniform surface. Uniform graphene films were found to grow on Ta films after exposure to both carbon sources at 1200°C but Raman measurements showed no signs of graphene on films exposed to the same temperature without a carbon flux.
Cu CMP Edge Uniformity Improvement Studies for 32 nm Technology Node and Beyond
Authors: Zhang John H , Economikos Laertis , Tseng Wei-tsu , Choi Jihong , Fang Qiang , Tang Teck Jung , Salfelder Joe , Truong Connie 
Published: August 2010

AbstractStudies of the wafer edge uniformity step by step, from hard mask deposition, reactive ion etch, electroplating to post Cu CMP had been done using scanning electron microscopy (SEM) measurements, showed that the major wafer non-uniformity comes from the Cu CMP step. Improvement of Cu CMP edge uniformity had been achieved through engineering of platen 1 using real time profile control as well as CMP head zone pressure adjustment and platen 3 slurry optimizations