Silicon Ingot Lifetime Tester for Large Crystals

Research output: Contribution to conferencePaper


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 languageAmerican English
Number of pages10
StatePublished - 1999
EventElectrochemical Society Joint Meeting - Honolulu, Hawaii
Duration: 17 Oct 199922 Oct 1999


ConferenceElectrochemical Society Joint Meeting
CityHonolulu, Hawaii

NREL Publication Number

  • NREL/CP-590-26499


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