Quantitative surface recombination imaging of single side processed silicon wafers obtained by photoluminescence modeling

Abstract

Characterizing the surface recombination of a silicon wafer is commonly performed by measuring the effective lifetime of a symmetrically processed sample and using simplified analytical models to derive a characteristic property of the recombination, such as the surface recombination factor J0s. The most widely used method is based on QSSPC measurements which require large, homogeneously processed areas and is valid only for uniform carrier distributions throughout the thickness of the sample. In this work we present an alternative method for deriving the surface recombination properties from photoluminescence (PL) images of single side processed wafers, where the rear side minority carrier density is pinned by a highly-recombining surface. By numerically modelling the photoluminescence signal and calibrating it against an independent and well characterized sample, PL images can be quickly converted into, for example, J0s images. We experimentally validate the method and show its robustness and limits by modelling the uncertainty of sample properties and measurement conditions. The method has the advantage of requiring minimal sample preparation. The use of an imaging technique allows numerous parameters to be characterized on a single sample, as is demonstrated by its application to laser-doped silicon.