Abstract
A lifetime-measurement instrument has been developed to characterize large silicon ingots prior to wafering and polishing. It uses the direct-current photoconductance decay method and localized probing and illumination to achieve the necessary sensitivity on low-resistivity, large samples. A 940-nm, 60-Wp, pulsed-laser diode beam (250-ms width, <100-ns cut-off) lights the as-cropped siliconsurface between two ohmic-contact probes. A user-friendly graphical interface supports data acquisition, lifetime calculation, and data storage. Pneumatic systems position the ingot and probes.Three-dimensional, finite-element analysis indicates that the detection depth of this technique is much better than the microwave or radio-frequency techniques. It also shows that the as-cropped surfacefinish is adequate for measuring bulk lifetimes on the order of 50 ms or less-a typical range for Czochralski ingots used in photovoltaic module production. Measurement repeatability and clear distinction among different grades of feedstock materials have been demonstrated.
Original language | American English |
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Number of pages | 10 |
State | Published - 1999 |
Event | Electrochemical Society Joint Meeting - Honolulu, Hawaii Duration: 17 Oct 1999 → 22 Oct 1999 |
Conference
Conference | Electrochemical Society Joint Meeting |
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City | Honolulu, Hawaii |
Period | 17/10/99 → 22/10/99 |
NREL Publication Number
- NREL/CP-590-26499