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

TL;DR

This paper provides a systematic theoretical analysis of steady-state minority carrier lifetime measurements, relating surface and bulk properties, and offers analytical solutions to distinguish intrinsic bulk lifetime from surface effects in semiconductor samples.

Contribution

It introduces a comprehensive theoretical framework and analytical solutions to relate measured lifetime to bulk properties, accounting for surface passivation and sample thickness.

Findings

Analytical solutions for passivated and unpassivated wafers and blocks.

Criterion for critical sample thickness to deduce bulk lifetime.

Method to separate surface effects from bulk properties in measurements.

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 wide range of samples such as ingots or wafers. In this work, a systematic theoretical analysis of the steady-state approach is presented. It is shown how the measured lifetime relates to the intrinsic bulk lifetime for a given material quality, sample thickness, and surface passivation. This makes the bulk properties experimentally accessible by separating them from the surface effects. In particular, closed analytical solutions of the most important cases, such as passivated and unpassivated wafers and blocks are given. Based on these results, a criterion for a critical sample thickness is given beyond which a lifetime measurement allows deducing the bulk properties for a given surface recombination. These results are of particular interest for semiconductor material diagnostics especially for photovoltaic applications but not limited to this field.