Influence of the NH3:SiH4 ratio and surface morphology on the surface passivation of phosphorus-diffused C-Si by PECVD SiNx

Yimao Wan, Di Yan, Andres Cuevas, Keith R. McIntosh

    Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

    4 Citations (Scopus)

    Abstract

    We investigate the surface passivation of phosphorus (n+) diffused crystalline silicon that is either planar or textured and passivated with amorphous silicon nitride (SiNx). A low and relatively constant saturation current density J0 is attained on the n+-diffused planar surfaces over a wide range of refractive index (n = 1.9-2.9 at 632 nm), and a wide range of sheet resistance (39-320 Ω/□). The results demonstrate that the trade-off between the optical transmission and surface recombination at n+-diffusion can be circumvented. That is, with careful optimization of SiNx properties, the optical advantages of SiNx can be enjoyed without penalty in recombination. In specific, on a light diffusion with sheet resistance of 700 Ω/□, a record-low J0 of 4 fA/cm2 is obtained using a nearly-stoichiometric SiNx with negligible absorption at short wavelengths. Moreover, it is shown that for lightly diffused surfaces, any additional recombination that occurs at textured surfaces relates strongly to the NH3:SiH4 ratio during the SiNx deposition, and consequently correlates inversely with n. In other words, an increase in the NH3:SiH4 ratio leads to an increase in recombination on planar wafers, and an even larger increase in recombination on textured wafers. By contrast, at the heavily-diffused surface, recombination at textured and planar wafers is approximately the same, irrespective of the NH3:SiH4 ratio. In summary, the results in this work indicate that the additional recombination invoked by the textured surfaces is greater as (i) the NH3:SiH4 ratio increases, which also increases n, and (ii) the phosphorus diffusion is lighter.

    Original languageEnglish
    Title of host publication2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014
    PublisherInstitute of Electrical and Electronics Engineers Inc.
    Pages3317-3321
    Number of pages5
    ISBN (Electronic)9781479943982
    DOIs
    Publication statusPublished - 15 Oct 2014
    Event40th IEEE Photovoltaic Specialist Conference, PVSC 2014 - Denver, United States
    Duration: 8 Jun 201413 Jun 2014

    Publication series

    Name2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014

    Conference

    Conference40th IEEE Photovoltaic Specialist Conference, PVSC 2014
    Country/TerritoryUnited States
    CityDenver
    Period8/06/1413/06/14

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