Interplay of bulk and surface properties for steady-state measurements of minority carrier lifetimes

Abstract

The measurement of the minority carrier lifetime is a powerful tool in the field of semiconductor material characterization as it is very sensitive to electrically active defects. Furthermore, it is applicable to a large variety of samples ranging from ingots to wafers. In this work, a systematic analysis of the effective measurable lifetime within the steady-state approach for samples of arbitrary thickness is presented and applied to experimental data. It is shown how the measured lifetime relates to the intrinsic bulk lifetime for a given material quality, sample thickness, and surface passivation. This approach makes the bulk properties experimentally accessible by separating them from the surface effects. A criterion for a critical sample thickness is given beyond which a lifetime measurement allows deducing the bulk properties for a given surface recombination. It is shown how the surface recombination effects lifetime measurements even for thick blocks. Furthermore, it is demonstrated under what conditions a lifetime measurement on unpassivated samples can give reliable bulk information. These results are of particular interest for semiconductor material diagnostics especially for photovoltaic applications but not limited to this field.