Some Challenges in Making Accurate and Reproducible Measurements of Minority Carrier Lifetime in High-Quality Si Wafers

Bhushan Sopori, Srinivas Devayajanam, Prakash Basnyat, Helio Moutinho, Bill Nemeth, Vincenzo Lasalvia, Steve Johnston, Jeff Binns, Jesse Appel

Research output: Contribution to conferencePaperpeer-review

6 Scopus Citations

Abstract

Measurement of the minority carrier lifetime (τ) of high-quality wafers (having bulk minority carrier lifetime, τb > few milliseconds) requires surface passivation with very low surface recombination velocity, typically < 1cm/s. Furthermore, for mapping large (e.g., 156 x156 mm) wafers, the passivation must also be stable and uniform over the entire wafer surfaces. These are very demanding requirements and it is a common experience that they are very difficult to achieve. Yet, they are necessary for performing defect analyses of the current N-type wafers. To understand the problems associated with these measurements, we have studied effect of wafer preparation (cleaning procedures, handling) and the passivation characteristics (stability, sensitivity to light, thickness of the passivation medium required for stable passivation) for many commonly used passivation media - iodine-ethanol (IE), quinhydrone-methanol (QHM), aluminum oxide (Al2O3), amorphous-silicon (a-Si), and silicon dioxide (SiO2). Here, we will discuss main factors that influence the accuracy and repeatability of lifetime measurements.

Original languageAmerican English
Pages649-654
Number of pages6
DOIs
StatePublished - 15 Oct 2014
Event40th IEEE Photovoltaic Specialist Conference, PVSC 2014 - Denver, United States
Duration: 8 Jun 201413 Jun 2014

Conference

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

Bibliographical note

Publisher Copyright:
© 2014 IEEE.

NREL Publication Number

  • NREL/CP-5J00-61222

Keywords

  • charge carrier lifetime
  • defects
  • oxidation
  • passivation
  • silicon

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