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Journal ArticleDOI

Catalytic chemical vapor deposition method to prepare high quality hydro‐fluorinated amorphous silicon

01 Dec 1988-Journal of Applied Physics (American Institute of Physics)-Vol. 64, Iss: 11, pp 6505-6509
TL;DR: In this paper, a new type of chemical vapor deposition method, named "Catalytic-CVD" method, is presented, in which deposition gases are decomposed by catalytic or pyrolytic reaction between deposition gases and a heated catalyzer, and films are thermally grown on a substrate at temperatures lower than 300°C without any help from glow discharge plasma.
Abstract: A new type of chemical vapor deposition method, named ‘‘Catalytic‐CVD’’ method, is presented. In the method, deposition gases are decomposed by catalytic or pyrolytic reaction between deposition gases and a heated catalyzer, and films are thermally grown on a substrate at temperatures lower than 300 °C without any help from glow discharge plasma. Hydro‐fluorinated amorphous silicon (a‐Si:F:H) films are deposited by this method using both a SiF2 and H2 gas mixture and a SiH2F2 and H2 mixture. It is found that a very high quality a‐Si:F:H film can be obtained, and for instance, that the photosensitivity for AM‐1 of 100 mW/cm2 exceeds 106 and the spin density is as low as 6×1015 cm−3.
Citations
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Journal ArticleDOI
TL;DR: In this paper, internal friction and shear modulus measurements of amorphous silicon and germanium (a-Si) films were performed and it was shown that hydrogenated a-Si with about 1 at. % H prepared by hot-wire chemical-vapor-deposition leads to an internal friction nearly three orders of magnitude smaller than observed for all other ammorphous solids.
Abstract: We present internal friction and shear modulus measurements of amorphous silicon (a-Si) and germanium (a-Ge) films. The temperature independent plateau in internal friction below 10 K, common to all amorphous solids, also exists in these films. However, its magnitude which depends critically on the deposition method is smaller than found for all other amorphous solids. In particular, hydrogenated a-Si with about 1 at. % H prepared by hot-wire chemical-vapor-deposition leads to an internal friction nearly three orders of magnitude smaller than observed for all other amorphous solids. The internal friction increases after the hydrogen is removed by effusion.

2 citations

Journal ArticleDOI
TL;DR: In this article, the ion-beam assisted deposition of SiF4, SiH4+Ar, or SiF 4+SiH4 as the gases for the ion source is described.
Abstract: a‐Si:F and a‐Si:F:H films have been prepared by ion‐beam‐assisted deposition using SiF4, SiH4+Ar, or SiF4+SiH4 as the gases for the ion source. Fluorine in a‐Si eliminates some dangling bonds, increases the optical gap, and decreases the dark conductivity. The results are influenced mainly by the ion‐beam energy used. The a‐Si:F films do not exhibit an activated conductivity even up to 150 °C, and no photoconductivity could be detected. However, film properties were significantly improved when a very small amount of H was added to the a‐Si:F and much less than 1 at. % H produced films that were photoconducting and had activated conductivities. The properties of these a‐Si:F:H are strongly dependent on both the fluorine concentration CF and the hydrogen concentration CH. The deposition rate decreases with increasing SiF4 content in the source gas, and neither CF nor CH vary linearly with the change in the source gas ratio SiH4/(SiF4+SiH4). Hence, CH must be known and controlled in order to evaluate the eff...

1 citations

Journal ArticleDOI
TL;DR: In this article, the optoelectronic and structural properties of a-Si:H deposited by Hot-Wire chemical vapor deposition (HW-CVD) from SiH4 and H2 at medium and high tungsten filament temperatures were studied.
Abstract: We present a study of the optoelectronic and structural properties of a-Si:H deposited by Hot-Wire chemical vapor deposition (HW-CVD) from SiH4 and H2 at “Medium” (Tfil ≃ 1500°C) and “high” (Tfil ≃ 1900 °C) filament temperatures. For each tungsten filament temperature regime, the following deposition parameters are varied: (i) pressure (p ∼ 10−2 — 0.5 Torr); (ii) substrate temperature (Tsub ∼ 180 — 270 °C); (iii) silane flow rate (FsiH4 ∼ 1 — 10 ccm) and (iv) hydrogen flow rate (FH2 ∼ 0 — 10 seem). Films deposited at Tfil ∼ 1900 °C in a low pressure regime (p ∼ 2.7 × 10−2Torr) using flows of 5 sccm for both H2 and SiH4 had high deposition rates (rd ∼ 8 As−1). These films showed an optical bandgap, E9Tauc ≃ 1.7 eV, a dark conductivity σd ∼ 10−8Scm−1 with an activation energy Eα,σd ≃ 0.8 eV, and photoconductivity σph ≥ 10−5Scm−1 (σph ∼ 10−5). Films deposited at Tju = 1500 °C and p ≃ 0.3 Torr, showed 1.7 < E9Tauc < 2 eV, 10−5 < σd < 10−3Scm−1, 0.2 < Eα,σ d < 0.5 eV and σph/Σd < 102. For the same Tfit and p ∼ 3 × 10−2 — 0.1 Torr, the films show 1.7 < E9Tauc < 2 eV, 10−3 < Σd < 10−1Scm−1 and σph/σd < 1. Films deposited using molybdenum and rhenium filaments at Tfil ≃ 1900 °C show E9Tauc ≃ 1.7 eV and σd ∼ σph ∼ 10−7Scm−1.

1 citations

Journal ArticleDOI
TL;DR: In this paper, the authors show that the optical bandgap increases with substrate temperature and the photoconductivity decreases with the substrate temperature, showing a complex dependence on substrate temperature (Tsub).
Abstract: Hydrogenated amorphous silicon, a-Si:H, is deposited from silane (SiH4) and hydrogen (H2) using a tungsten wire at low filament temperatures (Tfil = 1200 °C) by catalytic chemical vapor deposition. The deposition rate increases monotonically with the depositions pressures and shows a maximum at an H2: SiH4 flow ratio of unity. Vanishingly small deposition rates were observed for silane-only depositions and for H2-to-SiH4 flow ratios of 2.5 and above. The optoelectronic properties show complex dependence on substrate temperature (Tsub). Three intervals of Tsub with distinct optoelectronic were observed: as Tsub increases from 180 to 220 °C, the optical bandgap, % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB % PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0x % c9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8fr % Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGfb % Waa0baaSqaaiaadEgaaeaacaWGubWaaSbaaWqaaiaadggacaWG1bGa % am4yaaqabaaaaaaa!3D5C! $$E_g^{{T_{auc}}}$$ increases from 1.9 to 2.4 eV, the dark conductivity σd, decreases from 10−10 to 10−15 Ω−1cm−1 and the photoconductivity, σρh, decreases from 10−5 to 10−10 Ω−1cm−1 (region (i)). As Tsub increases from 220 to 250 °C, % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB % PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0x % c9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8fr % Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGfb % Waa0baaSqaaiaadEgaaeaacaWGubWaaSbaaWqaaiaadggacaWG1bGa % am4yaaqabaaaaaaa!3D5C! $$E_g^{{T_{auc}}}$$ decreases to 1.8 eV and the photosensitivity, σph/σd decreases to ~ 1 due to an increase of both σd and σph (region (ii)). Throughout these two regions, the photoconductivity γ factor remains between 0.6 and 0.9 and the activation energy of the dark conductivity, % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB % PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0x % c9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8fr % Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGfb % WaaSbaaSqaaiaadggacaGGSaGaeq4Wdm3aaSbaaWqaaiaadsgaaeqa % aaWcbeaaaaa!3D1B! $${E_{a,{\sigma _d}}}$$ , remains between 0.7 and 0.9 eV. Above 250 °C, the σp/h and σd remain approximately constant at 10−4 Ω−1cm−1 and γ decreases to below 0.5 and % MathType!MTEF!2!1!+- % feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqr1ngB % PrgifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0x % c9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8fr % Fve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGfb % WaaSbaaSqaaiaadggacaGGSaGaeq4Wdm3aaSbaaWqaaiaadsgaaeqa % aaWcbeaaaaa!3D1B! $${E_{a,{\sigma _d}}}$$ to ~ 0.3 eV.
Journal ArticleDOI
TL;DR: In this article, a hydrogenated amorphous silicon (a-Si:H) interface fabrication technology for the plasma CVD method, which can produce low interface defect density, is presented.
Abstract: A hydrogenated amorphous silicon (a-Si:H) interface fabrication technology for the plasma CVD method, which can produce low interface defect density, is presented. The relation between the interface defect density and radio frequency (RF) power was investigated. As a result, the difference between the interface defect density and the bulk defect density decreased with increasing the RF power. A high RF power (25 W) a-Si:H buffer layer 5 nm thick was deposited on the interface before depositing low RF power (5 W) a-Si:H layer with a low bulk defect density. It has been found that the ideal defect density distribution, which shows the uniform distribution with the very low defect density (4.2x10M cmJ) from the i/i interface to the bulk, can be accomplished by 5 nm buffer layer.
References
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Book
01 Jan 1962

1,204 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: 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.

151 citations

Journal ArticleDOI
TL;DR: Amorphous silicon (a•Si) films are deposited at about 320˚C by a new thermal chemical vapor deposition method as mentioned in this paper, where the gas mixture of intermediate species SiF2 and H2, decomposed thermally by the catalytic reaction, is used as a material gas.
Abstract: Amorphous silicon (a‐Si) films are deposited at about 320 °C by a new thermal chemical vapor deposition method. In this method, the gas mixture of intermediate species SiF2 and H2, decomposed thermally by the catalytic reaction, is used as a material gas. It is found that the photosensitivity of the a‐Si film for AM1 of 100 mW/cm2 exceeds over 106 and that the spin density is as low as 1.5×1016 cm−3 for the film deposited with a rate of several A/s.

114 citations