Dynamic photoluminescence lifetime imaging of multicrystalline silicon bricks

We apply the approach of dynamic photoluminescence lifetime imaging to a multicrystalline silicon brick. The dynamic approach allows the calibration-free determination of the bulk carrier lifetime of silicon bricks prior to wafer sawing. Using an indium gallium arsenide camera, we determine the bulk lifetime from the time-dependent luminescence emission for a modulated optical excitation. A ratio, including four photoluminescence images, acquired at different times during the modulated excitation, is calculated and found to depend on the camera integration time and the bulk lifetime. We demonstrate that the exact value of the surface recombination and the thickness of the brick are not required for the determination of the bulk carrier lifetime with the dynamic photoluminescence technique. The bulk lifetime is obtained locally by comparing the experimentally determined ratio with the simulated ratio for each image pixel. Since we are investigating the ratio of photoluminescence images containing information of the time dependence of the excess carriers, the doping-dependent luminescence emission has not to be corrected for the typical height-dependent doping variations. Therefore, the dynamic photoluminescence lifetime imaging technique is well suited for the investigation of bricks.