Micro-photoluminescence spectroscopy on metal precipitates in silicon

Metallic impurities are detrimental to many silicon devices and limit the efficiency of multi crystalline silicon solar cells. Therefore they are a major subject of ongoing research. Photoluminescence spectroscopy is a promising technique for detecting precipitated metals in silicon because of its sensitivity to the minority carrier density and to specific types of defects; however the impact of impurities on the defect luminescence could not be clarified yet. In this letter we examine the role of micron-sized iron and copper precipitates in direct bonded wafers by micro-photoluminescence spectroscopy. Both kinds of precipitates are detectable by means of the reduced band-to-band luminescence. An element-specific effect on the defect luminescence is observed. The results are confirmed by X-ray fluorescence spectroscopy.