Impurity and Defect Analysis in Solar Cell Si by Photoluminescence Spectroscopy and Topography

Prof Michio Tajima (Institute of Space and Astronautical Science/JAXA, Japan)

SOLAR SEMINAR SERIES

DATE: 2011-07-25
TIME: 14:00:00 - 15:00:00
LOCATION: Ian Ross Seminar Room
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ABSTRACT:
The photoluminescence (PL) technique has been used to analyze electrically active defects and impurities in multicrystalline silicon (mc-Si) for solar cells. PL imaging during HF etching has the advantage of very rapid detection of defects, which allows us to obtain numerous successive PL images of wafers positioned from the bottom to top of the mc-Si ingots, as well as to synthesize the three-dimensional distribution of the defects from the images. We showed the multiplication of dislocation clusters and their interaction with grain boundaries. The spectroscopic analysis of free and impurity-bound exciton luminescence at liquid He temperature enabled us to determine the impurity concentrations in electronic-grade Si, which has been standardized and used worldwide. We modified the technique to extend the concentration range to 1 x 1014 - 1 x 1017 cm-3 for the analysis of solar-grade mc-Si. Satisfactory agreement was obtained among PL, secondary ion mass spectroscopy and inductively coupled plasma mass spectroscopy.

BIO:
Michio Tajima received his Ph. D. degree from the University of Tokyo in 1975. Dr. Tajima joined Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency (ISAS/JAXA) in 1989 after 14 years with Electrotechnical Laboratory. Currently, he is Research Professor and Professor Emeritus at ISAS/JAXA, and Visiting Professor at Meiji University. He has engaged in the photoluminescence characterization of impurities and defects in technologically important semiconductor materials, such as silicon, silicon-on-insulator (SOI), silicon carbide and gallium arsenide. Dr. Tajima has been responsible for solar cells, batteries, and electronic devices for scientific satellites at ISAS/JAXA. His present area of specialization is characterization of multicrystalline Si for solar cells and SiC for power devices. Dr. Tajima served as Editor-in-Chief of Japanese Journal of Applied Physics (JJAP) in 1998-2000 and as Vice President of the Japan Society of Applied Physics in 2004-2006.