Conduction- and valence-band offsets at the hydrogenated amorphous silicon-carbon/crystalline silicon interface via capacitance techniques

Essick, John; Nobel, Zachariah; Li, Yuanmin; Bennett, M.

doi:10.1103/physrevb.54.4885

Cited by 29 publications

(9 citation statements)

References 10 publications

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“…In all these test structures, a 40 nm thick µc-Si:H layer grown with high hydrogen dilution warrants a low tunnelling resistance to the ZnO back contact. If we identify E a with the valence band offset ∆E V between the c-Si wafer and the (i) a-Si:H interlayer this result corresponds reasonably well to the band offset data reported earlier [2][3][4][5]. After a deposition time of t dep = 30 s we obtain for both types of contacts resistances R < 10 -2 Ωcm 2 , i.e., values that are very well suited for a low-ohmic back contact in a solar cell.…”

Section: Heterojunction C-si / (I) A-sisupporting

confidence: 90%

Resistive Losses at c-Si/a-Si:H/ZnO Contacts for Heterojunction Solar Cells

2007

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We study resistive losses at (p)c-Si/(p)Si:H/(n)ZnO heterojunction back contacts for high efficiency silicon solar cells. We find that a low tunnelling resistance for the (p)a-Si:H/(n)ZnO part of the junction requires deposition of Si:H with a high hydrogen dilution R H > 40 resulting in a highly doped µc-Si:H layer. Such a µc-Si:H layer if deposited directly on a Si wafer yields a surface recombination velocity of S ≈ 180 cm/s. Using the same layer as part of a (p)c-Si/(p)Si:H/(n)ZnO back contact in a solar cell results in an open circuit voltage V OC = 640 mV and a fill factor FF = 80 %. Insertion of an (i)a-Si-layer between the µc-Si:H and the wafer leads to a further decrease of S and, for the solar cells to an increase of V OC . However, if the thickness of this intrinsic layer exceeds a threshold of 4-5 nm, resistive losses lead to a degradation of the fill factor of the solar cells. These resistive losses result from a valence band offset ∆E V between a-Si:H and c-Si of about 600 meV. The fill factor losses overcompensate the V OC gain such that there is no benefit of the (i)a-Si:H interlayer for the overall solar cell performance when using an (i)a-Si:H/(p)µc-Si:H double layer.

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Section: Heterojunction C-si / (I) A-sisupporting

confidence: 90%

Resistive Losses at c-Si/a-Si:H/ZnO Contacts for Heterojunction Solar Cells

2007

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“…Published values are unfortunately widely spread [1][2][3][4], and mostly based on optical measurements; doubts have been expressed about their validity to be used in order to explain electrical phenomena.…”

Section: Introductionmentioning

confidence: 99%

Influence of the amorphous/crystalline silicon heterostructure properties on planar conductance measurements

Varache

Favre

Korte

et al. 2012

Journal of Non-Crystalline Solids

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“…% normally found in glow discharge deposited a-Si:H increases the optical gap of the amorphous semiconductor. 40 It is therefore reasonable that the hydrogen rich shell surrounding the silicon nanocrystal has a bandgap of approximately 2.0 eV. This is admittedly a rough estimate, but the exact value of the energy gap of the hydrogen rich shell surrounding the nanocrystal is not crucial for the argument below.…”

Section: Discussionmentioning

confidence: 98%

“…When the crystal fraction is 0.10, the dangling bond density as determined by the midgap optical absorption coefficient is ϳ3 ϫ 10 18 cm −3 , compared to roughly 10 17 cm −3 for the film with X c = 0.02 crystal fraction. 40 However, if 10% of the mixed-phase material is crystalline, then with nanoparticles of diameter ϳ5 nm, this implies a density of nanocrystalline inclusions of ϳ10 18 cm −3 . Consequently, the excess charges donated by these inclusions would not be sufficient to maintain the dark Fermi level at its position closer to the conduction band edge ͓see Fig.…”

Section: Discussionmentioning

confidence: 99%

Structural and electronic properties of dual plasma codeposited mixed-phase amorphous/nanocrystalline thin films

Adjallah

Anderson

Kortshagen

et al. 2010

Journal of Applied Physics

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A dual-plasma codeposition system capable of synthesizing thin films of mixed-phase materials consisting of nanoparticles of one type of material embedded within a thin film semiconductor or insulator matrix is described. This codeposition process is illustrated by the growth of hydrogenated amorphous silicon ͑a-Si:H͒ films containing silicon nanocrystalline inclusions ͑a/nc-Si:H͒. A capacitively coupled flow-through plasma reactor is used to generate silicon nanocrystallites of diameter 5 nm, which are entrained by a carrier gas and introduced into a capacitively coupled plasma enhanced chemical vapor deposition reactor with parallel plate electrodes, in which a-Si:H is synthesized. The structural and electronic properties of these mixed-phase a/nc-Si:H films are investigated as a function of the silicon nanocrystal concentration. At a moderate concentration ͑crystalline fraction 0.02-0.04͒ of silicon nanocrystallites, the dark conductivity is enhanced by up to several orders of magnitude compared to mixed-phase films with either lower or higher densities of nanoparticle inclusions. These results are interpreted in terms of a model whereby in films with a low nanocrystal concentration, conduction is influenced by charges donated into the a-Si:H film by the inclusions, while at high nanocrystal densities electronic transport is affected by increased disorder introduced by the nanoparticles.

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Conduction- and valence-band offsets at the hydrogenated amorphous silicon-carbon/crystalline silicon interface via capacitance techniques

Cited by 29 publications

References 10 publications

Resistive Losses at c-Si/a-Si:H/ZnO Contacts for Heterojunction Solar Cells

Resistive Losses at c-Si/a-Si:H/ZnO Contacts for Heterojunction Solar Cells

Influence of the amorphous/crystalline silicon heterostructure properties on planar conductance measurements

Structural and electronic properties of dual plasma codeposited mixed-phase amorphous/nanocrystalline thin films

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