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 language | American English |
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Pages | 689-692 |
Number of pages | 4 |
DOIs | |
State | Published - 1996 |
Event | Twenty Fifth IEEE Photovoltaic Specialists Conference - Washington, D.C. Duration: 13 May 1996 → 17 May 1996 |
Conference
Conference | Twenty Fifth IEEE Photovoltaic Specialists Conference |
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City | Washington, D.C. |
Period | 13/05/96 → 17/05/96 |
NREL Publication Number
- NREL/CP-22391