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Journal ArticleDOI

Catalytic Chemical Vapor Deposition (CTC–CVD) Method Producing High Quality Hydrogenated Amorphous Silicon

20 Dec 1986-Japanese Journal of Applied Physics (IOP Publishing)-Vol. 25, Iss: 12
TL;DR: In this article, a new method of producing high quality hydrogenated amorphous silicon (a-Si:H) films was presented, without using any plasmas or photochemical excitation, but using only thermal and catalytic reactions between deposition-gas and heated tungsten catalyzer.
Abstract: A new method of producing high quality hydrogenated amorphous silicon (a-Si:H) films is presented. An SiH4. and H2 gas mixture is decomposed without using any plasmas or photochemical excitation, but using only thermal and catalytic reactions between deposition-gas and a heated tungsten catalyzer. Photoconductivity of films produced by this methodreaches 10-3 (Ωcm)-1 and photosensitivity exceeds 105 for illumination of AM-1 light of 100 mW/cm2.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a simplified model for the deposition process is suggested based on this data and other information, and a novel substrate holder is used to control the growth of a•Si:H growth on nearby substrates.
Abstract: High‐quality hydrogenated amorphous silicon films (a‐Si:H) have been produced by decomposition of low‐pressure silane gas on a very hot surface with deposition on a nearby, typically 210 °C substrate. A high‐temperature tungsten filament provides the surface for heterogeneous thermal decomposition of the low‐pressure silane and subsequent evaporation of atomic silicon and hydrogen. These evaporated species (primarily) induce a‐Si:H growth on nearby substrates which are temperature controlled using a novel substrate holder. The light and dark conductivities, optical band gap, deposition rates, and light‐soaking effects of preliminary films are reported. The decomposition‐evaporation process has been examined using a mass spectrometer to directly detect the decomposition rate and the evaporated radical species. Based on this data and other information, a simplified model for the deposition process is suggested. The excellent film quality and the attributes of the deposition process make this technique, which was originally suggested by Wiessman, viable for the fast rate, large‐area deposition of a‐Si:H for solar cells and other applications.

195 citations

Journal ArticleDOI
TL;DR: In this paper, the absolute densities of H atoms produced in catalytic chemical vapor deposition (Cat-CVD or hot-wire CVD) processes were determined by employing two-photon laser-induced fluorescence and vacuum ultraviolet absorption techniques.
Abstract: The absolute densities of H atoms produced in catalytic chemical vapor deposition (Cat-CVD or hot-wire CVD) processes were determined by employing two-photon laser-induced fluorescence and vacuum ultraviolet absorption techniques. The H-atom density in the gas phase increases exponentially with increases in the catalyzer temperature in the presence of pure H2. When the catalyzer temperature was 2200 K, the absolute density in the presence of 5.6 Pa of H2 (150 sccm in flow rate) was as high as 1.5×1014 cm−3 at a point 10 cm from the catalyzer. This density is one or two orders of magnitude higher than those observed in typical plasma-enhanced chemical vapor-deposition processes. The H-atom density decreases sharply with the addition of SiH4. When 0.1 Pa of SiH4 was added, the steady-state density decreased to 7×1012 cm−3. This sharp decrease can primarily be ascribed to the loss processes on chamber walls.

144 citations

Journal ArticleDOI
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.

125 citations

Book ChapterDOI
01 Mar 2011
TL;DR: In this paper, the authors describe the diamond lattice of crystal silicon as a regular array or lattices, which must be consistent with the underlying chemical bonding properties of the atoms, such as the four covalent bonds of a silicon atom.
Abstract: Crystalline semiconductors are very well known, including silicon (the basis of the integrated circuits used in modern electronics), Ge (the material of the first transistor), GaAs and the other III-V compounds (the basis for many light emitters), and CdS (often used as a light sensor). In crystals, the atoms are arranged in near-perfect, regular arrays or lattices. Of course, the lattice must be consistent with the underlying chemical bonding properties of the atoms. For example, a silicon atom forms four covalent bonds to neighboring atoms arranged symmetrically about it. This “tetrahedral” configuration is perfectly maintained in the “diamond” lattice of crystal silicon.

114 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe how high-quality intrinsic hydrogenated amorphous silicon (a-Si: H), as well as purely intrinsic single-phase hydrogenated polycrystalline silicon (poly-Si, H), can be obtained by hot-wire chemical vapour deposition (HWCVD).
Abstract: We describe how high-quality intrinsic hydrogenated amorphous silicon (a-Si: H), as well as purely intrinsic single-phase hydrogenated polycrystalline silicon (poly-Si: H), can be obtained by hot-wire chemical vapour deposition (HWCVD). The deposition parameter space for these different thin-film materials has been optimized in the same hot-wire deposition chamber. A review of the earlier work shows how such high-quality films at both ends of the amorphous-crystalline scale have evolved. We incorporated both the amorphous and the polycrystalline silicon films in n-i-p solar cells and thin-film transistors (TFTs). The solar cells, with efficiencies in excess of 3%, confirm the material quality of both the a-Si: H and the poly-Si: H i-layer materials, but more work is needed to improve the interfaces with the doped layers. The TFTs made with a-Si: H and poly-Si: H channels show quite similar characteristics, such as a field-effect mobility of 0·5cm2 V−1 s−1, indicating that the channel region has a...

109 citations