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Journal ArticleDOI

Study on catalytic chemical vapor deposition method to prepare hydrogenated amorphous silicon

01 Jun 1989-Journal of Applied Physics (American Institute of Physics)-Vol. 65, Iss: 11, pp 4396-4402
TL;DR: In this paper, a new type of thermal chemical vapor deposition (CVD) method is presented, where material gases are decomposed by catalytic or pyrolytic reaction with a heated catalyzer, so that films can be deposited at temperatures less than 300°C without any plasma or photochemical excitation.
Abstract: A new type of thermal chemical vapor deposition (CVD) method is presented. In the method, material gases are decomposed by catalytic or pyrolytic reaction with a heated catalyzer, so that films can be deposited at temperatures less than 300 °C without any plasma or photochemical excitation, and the method is particularly called ‘‘Catalytic‐CVD.’’ Hydrogenated amorphous silicon films are deposited by this method, and the deposition mechanism is also investigated. It is found that device‐quality amorphous silicon films can be obtained and that inactive species, which are generated at the catalyzer and transported without gas‐phase reactions, are key species to make a high‐quality film by this method.
Citations
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Journal ArticleDOI
TL;DR: In this paper, it was shown that hydrogenated amorphous silicon containing as little as 1/10 the bonded H observed in device-quality glow discharge films have been deposited by thermal decomposition of silane on a heated filament.
Abstract: Device‐quality hydrogenated amorphous silicon containing as little as 1/10 the bonded H observed in device‐quality glow discharge films have been deposited by thermal decomposition of silane on a heated filament. These low H content films show an Urbach edge width of 50 mV and a spin density of ∼1/100 as large as that of glow discharge films containing comparable amounts of H. High substrate temperatures, deposition in a high flux of atomic H, and lack of energetic particle bombardment are suggested as reasons for this behavior.

464 citations

BookDOI
01 Jan 2012
TL;DR: In this paper, a-Si:H/c-Si heterojunction and other high efficiency solar cells: a comparison of rear contact cells are presented. But the authors do not provide a detailed description of the interaction between the two heterojunctions.
Abstract: Foreword.- Introduction.- Status of heterojunction solar cell R&D.- Basic features of Heterojunctions illustrated by selected experimental methods and results.- Deposition methods of thin film silicon.- Electronic properties of ultrathin a-Si:H layers and the a-Si:H/c-Si interface.- Degradation of (bulk and thin film) a-Si and interface passivation.- Photoluminescence and electroluminescence for a Si:H/c Si device and interface characterization.- Deposition and properties of transparent conductive oxides.- Metallization and formation of contacts.- Electrical and optical characterization of a-Si:H/c Si cells.- Wet-chemical pre-treatment of c Si for a-Si:H/c-Si heterojunctions.- Theory of heterojunctions and the determination of band offsets from electrical measurements.- Modeling and simulation of a Si:H/c Si cells.- Surface passivation using ALD Al2O3.- Introduction to AFORS-HET.- Hands-on experience with simulation tools.- a-Si:H/c-Si heterojunction and other high efficiency solar cells: a comparison.- Rear contact cells.- Progress in systematic industrialization of Hetero-Junction-based Solar Cell technology.

190 citations

Journal ArticleDOI
TL;DR: In this article, the influence of various deposition parameters on the deposition rate and the material properties was systematically investigated, and it was shown that the deposition performance of solar cells is determined by the product of the chemical reaction at the filament and the gas phase.
Abstract: Microcrystalline silicon (μc-Si:H) of superior quality can be prepared using the hot-wire chemical-vapor deposition method (HWCVD). At a low substrate temperature (TS) of 185 °C excellent material properties and solar cell performance were obtained with spin densities of 6×1015cm−3 and solar cell efficiencies up to 9.4%, respectively. In this study we have systematically investigated the influence of various deposition parameters on the deposition rate and the material properties. For this purpose, thin films and solar cells were prepared at specific substrate and filament temperatures and deposition pressures (pD), covering the complete range from amorphous to highly crystalline material by adjusting the silane concentration. The influence of these deposition parameters on the chemical reactions at the filament and in the gas phase qualitatively explains the behavior of the structural composition and the formation of defects. In particular, we propose that the deposition rate is determined by the product...

99 citations

Journal ArticleDOI
TL;DR: In this paper, a silane-hydrogen mixture was used in a hot-wire CVD reactor to produce polycrystalline silicon films at moderate substrate temperatures (280-500° C).
Abstract: Silicon films were deposited at moderate substrate temperatures (280–500° C) from pure silane and a silane-hydrogen mixture (10% SiH4, 90% H2) in a hotwire CVD reactor. The morphology, structure and composition of the samples were studied with scanning electron microscopy, transmission electron microscopy, transmission electron diffraction, X-ray diffraction, Raman spectroscopy and secondary ion mass spectrometry. The sample deposited at 500° C with pure silane has an amorphous structure, whereas the samples obtained from silane diluted in hydrogen have a polycrystalline structure, even that grown at the lowest temperature (280° C). Polycrystalline samples have a columnar structure with 0.3–1 μm crystallite sizes with preferential orientation in [220] direction. Deposition rates depend on the filament-substrate distance and range from 9.5 to 37 A/s for the polycrystalline samples. The high quality of the polycrystalline samples obtained makes the hot-wire technique very promising. Moreover, it is expected to be easily scaled up for applications to large-area optoelectronic devices and to photovoltaic solar cells.

81 citations

Journal ArticleDOI
TL;DR: In this paper, the catalytic chemical vapor deposition method is applied to obtain silicon nitride insulating films usable in large-scale integrated circuits, and it is found that the resistivity, the breakdown electric field, and also the hydrogen content of the films can be almost equivalent to those of the silicon dioxide films deposition at 700 °C or more, and their step coverage appears sufficient to apply them on device fabrication.
Abstract: The catalytic chemical vapor deposition method is applied to obtain silicon nitride insulating films usable in large‐scale integrated circuits. A N2 H4, N2 , and SiH4 gas mixture is decomposed by the catalytic or pyrolytic reaction with a heated catalyzer placed near substrates, and thus silicon nitride films are deposited at low temperatures around 300 °C with deposition rates higher than several hundreds A/min, without any help from plasma and photochemical excitation. It is found that the resistivity, the breakdown electric field, and also the hydrogen content of the films can be almost equivalent to those of the films deposited by the thermal chemical vapor deposition at 700 °C or more, and that their step coverage appears sufficient to apply them on device fabrication.

75 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a new reversible photoelectronic effect was reported for amorphous Si produced by glow discharge of SiH4, where long exposure to light decreases both the photoconductivity and the dark conductivity.
Abstract: A new reversible photoelectronic effect is reported for amorphous Si produced by glow discharge of SiH4. Long exposure to light decreases both the photoconductivity and the dark conductivity, the latter by nearly four orders of magnitude. Annealing above 150 °C reverses the process. A model involving optically induced changes in gap states is proposed. The results have strong implications for both the physical nature of the material and for its applications in thin‐film solar cells, as well as the reproducibility of measurements on discharge‐produced Si.

2,673 citations

Journal ArticleDOI
TL;DR: In this paper, a theory for a random mixture is given, based on the assumption that each crystal acts as if surrounded by a homogeneous medium whose properties are those of the mixture.
Abstract: The existing theories of the resistivity of mixtures assume regular arrangements of the two components, rather than random mixtures. A theory for a random mixture is given, based on the assumption that each crystal acts as if surrounded by a homogeneous medium whose properties are those of the mixture. Comparisons with experiment are made. The experimental data that have been examined fall roughly into two classes. One class consists of mixtures, where the variation of resistivity with composition disagrees violently with this theory, making it clear that the assumptions made are completely inapplicable. The remaining class consists of mixtures which generally agree well with the theory.

1,611 citations

Journal ArticleDOI
J. Tauc1
TL;DR: In this paper, a simple model based on the existence of internal electric fields is suggested to explain the exponential part of the absorption edge observed in many amorphous semiconductors.

1,150 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that substitutional doping of an amorphous semiconductor is possible and can provide control of the electronic properties over a wide range, which corresponds to a movement of the Fermi level of 1·2 eV.
Abstract: It is shown that substitutional doping of an amorphous semiconductor is possible and can provide control of the electronic properties over a wide range. a-Si and Ge specimens have been prepared by the decomposition of silane (or germane) in a radio-frequency (r.f.) glow discharge. Doping is achieved by adding carefully measured amounts of phosphine or diborane, between 5 × 10−6 and 10−2 parts per volume, to obtain n- or p-type specimens. The room temperature conductivity of doped a-Si specimens can be controlled reproducibly over about 10 orders of magnitude, which corresponds to a movement of the Fermi level of 1·2 eV. Ion probe analysis on phosphorus doped specimens indicates that about half the phosphine molecules in the gaseous mixture introduce a phosphorus atom into the Si random network; it is estimated that 30–40% of these will act as substitutional donors. The results also show that the number of incorporated phosphorus atoms saturates at about 3 × 1019 cm−3, roughly equal to the number ...

624 citations

Journal ArticleDOI
TL;DR: The hydrogen content of two series of a-Ge:H and a-Si:H samples prepared by sputtering with different partial pressures of H2 in Ar has been investigated by nuclear reaction techniques, gas evolution, and infrared absorption (wagging and stretching modes) as mentioned in this paper.
Abstract: The hydrogen content of two series of a-Ge:H and a-Si:H samples prepared by sputtering with different partial pressures of H2 in Ar has been investigated by nuclear reaction techniques, gas evolution, and infrared absorption (wagging and stretching modes).

261 citations