Structural, electrical, and optical properties of<i>a</i>-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Si</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mi mathvariant="normal">−</mml:mi><mml:mi mathvariant="normal">x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ge</mml:mi></mm

Mackenzie, Kenneth D.; Eggert, J. R.; Leopold, D. J.; Li, Y. M.; Lin, Showe‐Mei; Paul, William

doi:10.1103/physrevb.31.2198

Cited by 268 publications

(84 citation statements)

References 64 publications

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“…As is commonly found for a-SiGe:H materials and cells (Mackenzie et al 1985, Guha et al 1981, particularly for those made at high rates, use of high substrate temperatures and large amounts of hydrogen dilution are important to obtain good film quality and high cell efficiencies.…”

Section: Variation In Cell Properties With Different Deposition Condimentioning

confidence: 99%

Use of very-high-frequency plasmas to prepare a-Si:H-based triple-junction solar cells at high deposition rates: Annual technical status report, 11 March 1998--11 March 1999

Jones¹,

Liu²,

Tsu³

et al. 1999

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Corp. are gratefully acknowledged. We would like to specially thank Professor Xunming Deng for the many discussions and input he has made in advancing this program he previously led. 2 Executive Summary ObjectivesThe main objective of this program is to develop a high rate thin film deposition method in order to increase the throughput of ECD's roll-to-roll solar module production design and in doing so reduce the cost of the solar modules. In particular, a very high frequency (70 MHz) plasma enhanced chemical vapor deposition (PECVD) process is being developed for the fabrication of intrinsic layers for high efficiency amorphous silicon-based triple-junction solar cells at high deposition rates. Intrinsic layers consisting of either amorphous silicon or amorphous silicon germanium alloy materials are being developed. The program goal is to prepare these materials at rates of 10 Å/s or higher while maintaining the cell efficiencies at the high values presently obtained for devices made using the standard 13.56 MHz frequency and low deposition rates (near 1 Å/s). Upon completion of a successful program, this high rate process will be added to ECD's roll-to-roll solar cell production design to reduce solar module cost. ApproachIn order to test the feasibility of using the VHF method for high rate intrinsic layer preparation, the deposition conditions used to prepare small area (0.25 cm 2 ) single-junction amorphous silicon (a-Si:H) and silicon germanium alloy (a-SiGe:H) cells by the very high frequency (VHF) technique are being optimized to obtain the highest cell efficiencies. These component cells will then be combined to create high efficiency a-Si:H/a-SiGe:H/a-SiGe:H triple-junction cells. The deposition conditions for these multi-junction cells will also be optimized to further increase the device performance. In particular for the triple-junction cells, the conditions used to prepare p/n tunnel junctions will be optimized to minimize absorption and series resistance and maximize carrier collection and cell performance. Besides achieving high small area cell performance, large area cathode hardware designs which will allow for the uniform deposition of i-layers over a large area using the VHF technique and high deposition rates will be tested using a single chamber vacuum system. This large area hardware will be required for the future incorporation of the technique into an ECD built roll-to-roll solar cell production line. Results/StatusThe following has thus far been achieved during this year: 1) 8.0% stable efficiencies have been achieved for a-Si:H single-junction cells whose i-layers are prepared at rates near 10 Å/s using the VHF technique. This performance compares with 8.2% stabilized efficiencies for a-Si:H cells made using the same deposition equipment, the standard 13.56 MHz technique and deposition rates near 1 Å/s. While we have yet to achieve the 8.4% program goal for the a-Si:H cells, we hope that our recent improvement of the n-layer conditions as well as further optimization of other depositi...

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Section: Variation In Cell Properties With Different Deposition Condimentioning

confidence: 99%

Use of very-high-frequency plasmas to prepare a-Si:H-based triple-junction solar cells at high deposition rates: Annual technical status report, 11 March 1998--11 March 1999

Jones¹,

Liu²,

Tsu³

et al. 1999

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“…The most notable change is a narrowing of the bandgap with increasing Ge content. The mobility gap of a-Si 1Àx Ge x :H, that is the energy region containing localised states between the conduction and valence bands, decreases linearly with x from 1.8 eV for a-Si:H to 1.0 eV for a-Ge:H [7]. As the mobility gap narrows, the Fermi level does not maintain the same relative position between the bands, but instead tracks the conduction band mobility edge for x in the range 0.1-0.7 [7,8].…”

Section: Influence Of Gementioning

confidence: 99%

“…The mobility gap of a-Si 1Àx Ge x :H, that is the energy region containing localised states between the conduction and valence bands, decreases linearly with x from 1.8 eV for a-Si:H to 1.0 eV for a-Ge:H [7]. As the mobility gap narrows, the Fermi level does not maintain the same relative position between the bands, but instead tracks the conduction band mobility edge for x in the range 0.1-0.7 [7,8]. Since electrons are the majority carrier, the conductivity activation energy remains at 0.75-0.7 eV for a wide range of alloy compositions despite the changes in the mobility gap.…”

Section: Influence Of Gementioning

confidence: 99%

1∕f noise in hydrogenated amorphous silicon–germanium alloys

Johanson

Güneş

Kasap

2003

IEE Proc., Circuits Devices Syst.

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Measurements were made of conductance noise of a-Si:H and a-Si 1Àx Ge x :H in two different geometries: one where the current flow is transverse to the surface and the other where it is longitudinal to the surface. Because of the large change in sample resistance between the two geometries, it was not possible to measure both geometries at the same temperature. For both geometries, alloyinzg with up to 40% Ge reduces the noise magnitude by several orders of magnitude over that found in a-Si:H. The decrease is incompatible with several popular noise models. Extrapolating the temperature trends for each geometry shows that it is possible that the noise observed in the transverse samples has the same origin as the higher frequency part of the double power law spectra observed in the longitudinal samples.

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“…Amorphous hydrogenated binary Si-Ge alloy films (a-Si1-x Ge:H) have recently been investigated extensively and are expected to be a useful optoelectronic material for λ > 700 nm [1][2][3][4][5]. Introduction of Ge reduces the optical gap below 1.8eV, typical for a-Si:H and better matches the optical gap for the solar radiation spectum.…”

mentioning

confidence: 99%

“…Most of Si-Ge alloy films are deposited by the glow discharge decomposition of a gas mixture of SiΗ4 and GeH4 [1][2][3], [5]. However, this method has several drawbacks such as the poisonous and inflammable nature of the reactive gases and the poor control of the hydrogen content in the film.…”

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confidence: 99%

Electrical Properties of Hydrogenated Amorphous Si_1-xGe_xThin Films

Pisarkiewicz¹,

Stapiński²,

Kołodziej³

1991

Acta Phys. Pol. A

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Thin films of hydrogenated amorphous Si-Ge alloys were obtained by r.f. sputtering in Ar + H2 gas atmosphere using composite targets of Si and Ge. Dark conductivity and photoconductivity were measured in the temperature range of 300-500 K for films with x varying from 0.11 to 0.63. Both dark conductivity and photoconductivity exibit activation type dependences in the temperature range studied. Heterogeneity two-phase model and a model based on Fermi level shift with temperature were invoked to discuss the conduction mechanism.

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Structural, electrical, and optical properties ofa-Si1−xGe

Cited by 268 publications

References 64 publications

Use of very-high-frequency plasmas to prepare a-Si:H-based triple-junction solar cells at high deposition rates: Annual technical status report, 11 March 1998--11 March 1999

Use of very-high-frequency plasmas to prepare a-Si:H-based triple-junction solar cells at high deposition rates: Annual technical status report, 11 March 1998--11 March 1999

1∕f noise in hydrogenated amorphous silicon–germanium alloys

Electrical Properties of Hydrogenated Amorphous Si_1-xGe_xThin Films

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Structural, electrical, and optical properties ofa-Si1−xGe

Cited by 268 publications

References 64 publications

Use of very-high-frequency plasmas to prepare a-Si:H-based triple-junction solar cells at high deposition rates: Annual technical status report, 11 March 1998--11 March 1999

Use of very-high-frequency plasmas to prepare a-Si:H-based triple-junction solar cells at high deposition rates: Annual technical status report, 11 March 1998--11 March 1999

1∕f noise in hydrogenated amorphous silicon–germanium alloys

Electrical Properties of Hydrogenated Amorphous Si1-xGexThin Films

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Electrical Properties of Hydrogenated Amorphous Si_1-xGe_xThin Films