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Journal ArticleDOI

Hydrogenated Amorphous Silicon Thin-Film Deposition by Direct Photo-Enhanced Decomposition of Silane Using an Internal Hydrogen Discharge Lamp.

01 Jan 1986-MRS Proceedings (Springer Science and Business Media LLC)-Vol. 70, Iss: 1, pp 31-35
TL;DR: In this paper, a photo-enhanced decomposition of amorphous silicon (a-Si:H) thin-film transistors using a hydrogen discharge lamp is described.
Abstract: Hydrogenated amorphous silicon (a-Si:H) thin films have been deposited from silane using a novel photo-enhanced decomposition technique. The system comprises a hydrogen discharge lamp contained within the reaction vessel; this unified approach allows high energy photon excitation of the silane molecules without absorption by window materials or the need for mercury sensitisation. The film growth rates (exceeding 4 Angstrom/s) and material properties obtained are comparable to those of films produced by plasma-enhanced CVD techniques. The reduction of energetic charged particles in the film growth region should enable the fabrication of cleaner semiconductor/insulator interfaces in thin-film transistors.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the photo and dark conductivities (σph,σd) of the semiconductor layers are determined by the substrate temperature, and they are semiquantitatively discussed in terms of ArF laser photolysis of disilane, gas heating by heat flow from the substrate and laser irradiation, diffusion and gas phase polymerization.
Abstract: ArF laser-induced CVD has been employed to generate hydrogenated amorphous silicon (a-Si:H) from Si2H6 gas dilute with He, Ar, or H2. The formation of amorphous films or powder is found to depend critically on the kind of buffer gas, the stationary total and partial gas pressures, and the substrate temperature. These dependences have been investigated in the 1–5 Torr pressure and 100–400 °C temperature ranges. They are semiquantitatively discussed in terms of ArF laser photolysis of disilane, gas heating by heat flow from the substrate and laser irradiation, diffusion, and gas phase polymerization. Furthermore, photo ionization has been observed but found irrelevant for the a-Si:H layer properties. The photo and dark conductivities (σph,σd) of the semiconductor layers are determined by the substrate temperature. Theσph values range between 10−7 and 10−4 Ω−1 cm−1 and theσd values between 10−11 and 10−8 Ω−1 cm−1. The maximum ratioσph/σd amounts to 4×104. The layers are further characterized by their optical band gap and activation energy. The layer properties are compared to literature values of amorphous films prepared by various photo, HOMO, and plasma CVD methods.

23 citations

Journal ArticleDOI
TL;DR: In this article, two different types of a large-area high-intensity VUV dielectric-barrier discharge lamp for VUV emission have been constructed and operated over a wide range of voltage (0.5-20 kV).

23 citations

Journal ArticleDOI
01 Oct 1990
TL;DR: In this paper, a discussion on hydrogenated amorphous silicon (a-Si:H) film preparation by laser induced chemical vapor deposition (LICVD) using a pulsed CO2-laser in a parallel configuration is given.
Abstract: The following work gives a discussion on hydrogenated amorphous silicon (a-Si:H) film preparation by laser induced chemical vapor deposition (LICVD) using a pulsed CO2-laser in a parallel configuration. Deposition rate and initiation of polymerization were studied as a function of total pressure, gas flow, gas mixture (buffer gas, silane and/or disilane), substrate temperature, and radiation flux. The results lead to a reaction model where higher silane homologues play an important role for the film production. The film properties strongly depend on the substrate temperature Ts. The activation energy Ea of the dark conductivity decreases from 1.1 eV to 0.7 eV for films prepared at Ts = 230°C to 450°C. In the same temperature range, the dark conductivity σd increases from ∼10−14 to ∼10−10 (Ω cm)−1, whereas the photo conductivity σph shows a maximum of ∼10−6 (Ω cm)−1 at Ts = 320-330°C. These values, especially their temperature behaviour, are compared with the results of other CO2-LICVD works and further production methods. It is shown that the film formation depends on the gas phase chemistry as well as on the substrate temperature.

8 citations

Journal ArticleDOI
TL;DR: In this paper, a photo-CVD apparatus was built to deposit a-Si: H films and other kinds of amorphous thin films by a technique which is both simple and versatile.

8 citations

Journal ArticleDOI
TL;DR: In this article, a vacuum UV-photo-CVD reactor for direct decomposition of Si2H6, SiH4, GeH4 and B2H4 has been operated with a large area dielectric-barrier discharge lamp emitting excimer radiation.
Abstract: A vacuum UV-photo-CVD reactor for direct decomposition of Si2H6, SiH4, GeH4, and B2H6 for a-Si:H, a-Ge:H, and a-SiGe:H deposition has been operated with a large area dielectric-barrier discharge lamp emitting excimer radiation of Xe (7.3eV), Kr (8.6eV), or Ar (9.8eV). It is shown that the deposition process (Si2H6 or GeH4 at 0.5 mbar) is governed by the diffusion of long-lifetime radicals. High quality undoped and p-type doped a-Si:H has been deposited from Si2H6 and B2H6 with the Xe lamp spectrum (σph/σ≈106 at Eg=1.9eV) and film growth rates of up to 5 nm/min have been achieved.

7 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 article, a photo-CVD undoped and P-doped solar cell was fabricated using undoped amorphous silicon films and showed a conversion efficiency of 4.39% under AM1 insolation.
Abstract: Hydrogenated amorphous silicon films have been deposited by mercury photosensitized decomposition (photochemical vapor deposition: photo‐CVD) of disilane at a substrate temperature below 300 °C. The structural and optical properties of undoped films are very similar to those of films deposited by rf glow discharge decomposition. The electronic property measurement shows that the conductivity strongly depends on the substrate temperature during deposition. The photoconductivity reaches 5.7×10−3 (Ω cm)−1 (AM1,100 mW/cm2) at a substrate temperature of 200 °C. The dark conductivity is 10−6–10−8 (Ω cm)−1 and the Fermi level is located near the middle of the gap. n‐type doping has been also achieved by adding phosphine as an impurity to disilane. Furthermore, a p‐i‐n a‐Si solar cell was fabricated using photo‐CVD undoped and P‐doped films. The initial cell showed a conversion efficiency of 4.39% under AM1 insolation.

56 citations

Journal ArticleDOI
TL;DR: Amorphous silicon films have been prepared through mercury-photosensitized decomposition of monosilane gas at low temperatures as discussed by the authors, and they show optical and electrical properties comparable with those of the best films prepared by plasma chemical vapor deposition.
Abstract: Amorphous silicon films have been prepared through mercury‐photosensitized decomposition of monosilane gas at low temperatures. The films show optical and electrical properties comparable with those of the best films prepared by plasma chemical vapor deposition. The feasibility of amorphous solar cells with short‐circuit current densities of more than 10 mA/cm2 has been demonstrated by fabrication of a Schottky barrier structure.

55 citations

Journal ArticleDOI
TL;DR: In this article, a photochemical vapor deposition of a-Si films at a high rate using SiH 4 and a 185 nm low pressure mercury lamp was described, achieving a maximum rate of 1 nm/sec.
Abstract: Photochemical vapor deposition of a-Si films at a high rate using SiH 4 and a 185 nm low pressure mercury lamp is described. A maximum rate of 1 nm/sec was attained using the 185 nm lamp. This rate was about ten times higher than that using a 254 nm lamp. Assuming that there is no interaction between the effects of the two wavelengths, the deposition rate per light output power of 184.9 nm light is 160 times larger than that for 253.7 nm light. The absorption cross-section of the 184.9 nm light is ten times greater than that for the 253.7 nm light.

19 citations

Journal ArticleDOI
TL;DR: In this article, high quality a-Si:H films have been prepared by the direct photolysis of disilane at a substrate temperature below 350 °C, and the growth rate is independent of substrate temperature for both undoped and phosphorus doped films.
Abstract: High quality a-Si:H films have been prepared by the direct photolysis of disilane at a substrate temperature below 350 °C. The growth rate is independent of substrate temperature for both undoped and phosphorus doped films, while it is thermally activated and dramatically enhanced by boron doping. The hydrogen content decreases from 7 to 2 at.%, as deposition temperature is varied from 200 to 300 °C. The photoconductivity as high as 3.7 × 10 −4 Ω −1 cm −1 (AM1 100 mW/cm 2 ) has been obtained and no light soak degradation was observed.

18 citations