On the method of photoluminescence spectral intensity ratio imaging of silicon bricks: Advances and limitations

Abstract

Spectral photoluminescence imaging is able to provide quantitative bulk lifetime and doping images if applied on silicon bricks or thick silicon wafers. A comprehensive study of this new method addresses previously reported artefacts in low lifetime regions and provides a more complete understanding of the technique. Spectrally resolved photoluminescence measurements show that luminescence originating from sub band gap defects does not cause those artefacts. Rather, we find that optical light spreading within the silicon CCD is responsible for most of the distortion in image contrast and introduce a method to measure and remove this spreading via image deconvolution. Alternatively, image blur can be reduced systematically by using an InGaAs camera. Results of modelling this alternative camera type and experiments are shown and discussed in comparison. In addition to eliminating the blur effects, we find a superior accuracy for lifetimes above 100 μs with significantly shorter, but dark noise limited exposure times.