Surface Segregation as a Means of Gettering Cu in Liquid-Phase-Epitaxy Silicon Thin Layers Grown from Al-Cu-Si Solutions

    Research output: Contribution to conferencePaper

    Abstract

    We demonstrate that, by using the natural surface segregation phenomenon, Cu can be gettered to the surface from the bulk of silicon layers so that its concentrations in the liquid-phase-epitaxy (LPE) layers are much lower that its solubility at the layer growth temperature and the reported 10/sup 17/ cm/sup -3/ degradation threshold for solar-cell performance. Secondary-ion mass spectroscopy(SIMS) analysis indicates that, within a micron-deep sub-surface region, Cu accumulates even in as-grown LPE samples. Slower cooling after growth to room tempertaure enhances this Cu enrichment. X-ray photoelectron spectroscopy (XPS) measurement shows as much as 3.2% Cu in a suface region of about 50 .ANG. More surface-sensitive, ion-scattering spectrosopy (ISS) analysis further reveals about 7%of Cu at the top surface. These results translate to an areal gettering capacity of about 1.0 x 10/sup 16/ cm/sup -2/, which is higher that the available total-area density of Cu in the layer and substrate (3.6 x 10/sup 15/ cm /sup -2/ for a uniform 1.2 x 10 /sup17/ cm /sup-3/ Cu throughout the layer and substrate with a total thickness of 300 .mu.m).
    Original languageAmerican English
    Pages689-692
    Number of pages4
    DOIs
    StatePublished - 1996
    EventTwenty Fifth IEEE Photovoltaic Specialists Conference - Washington, D.C.
    Duration: 13 May 199617 May 1996

    Conference

    ConferenceTwenty Fifth IEEE Photovoltaic Specialists Conference
    CityWashington, D.C.
    Period13/05/9617/05/96

    NREL Publication Number

    • NREL/CP-22391

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