Relationship of Band-Edge Luminescence to Recombination Lifetime in Silicon Wafers

In recent years, intrinsic luminescence has been used as a method to characterize the recombination lifetime of crystalline silicon. The assumption is that the steady-state intrinsic photoluminescence at 1.09 eV (1.134 μm) can be related to the recombination lifetime. In this work, we measured the band-edge photoluminescence (PL) intensities of a number of single-crystal wafers. The resistivity in the wafer set ranges from 1 to 11,000 ohm-cm under constant excitation intensity. We then measured the PL spectra and recombination lifetimes of these wafer sets under a variety of conditions. The lifetime was measured using resonant-coupled photoconductive decay (RCPCD) in both air ambient and an iodine/methanol solution. The same procedure was used for the PL spectra. Plots of the measured lifetime versus the PL intensity showed weak correlation between the two quantities in air ambient. However, there is a positive relationship between the near-bandgap PL intensity and the recombination lifetime for passivated surfaces. Some fundamental physical reasons will be used to explain these results.