The lifetime distribution of multicrystalline Si wafers was imaged by means of calibrated measurements of the free-carrier emission using an infra-red camera. The spatially resolved lifetime measurements were performed as a function of the light-generated excess carrier density, showing a pronounced increase in lifetime with decreasing injection density at very low injection levels. Two theoretical models were applied to describe the abnormal lifetime increase: minority-carrier trapping and depletion region modulation around charged bulk defects. The trapping model was found to give better agreement with the experimental data. By fitting the trapping model to each point of the lifetime image recorded at different injection levels, a trap density mapping was generated. On multicrystalline Si wafers a clear correlation was found between trap and dislocation density mappings.

Defect Imaging in Multicrystalline Silicon Using a Lock-In Infrared Camera Technique. P.Pohl, J.Schmidt, C.Schmiga, R.Brendel: Journal of Applied Physics, 2007, 101[7], 073701