Discipline: Technology & Engineering
Subcategory: STEM Research
- Lincoln University (PA)
Co-Author(s): Uchechi Anyanwu and Andrey Semichaevsky , Lincoln University, Lincoln University, PA
Band-to-band photoluminescence from polycrystalline Si can be used to estimate local carrier densities in semiconductor samples. Under this approach, light consisting of photons of energies that exceed the bandgap of the material is shone on a sample. The excited electrons recombine with the holes at the rates that are proportional to the product of electron and hole concentrations, n*p. However, other recombination mechanisms such as excitation-dependent Shockley-Reed-Hall non-radiative (NR) recombination result in the reduced local radiative recombination rates. It is interesting to know how the carrier lifetimes that come from transient photoconductivity measurements compare with the estimated recombination rates.
In this work, we deduce the local NR recombination rates from the PL images and find correlations between them and our intensity-dependent measurements of minority carrier lifetimes for the same samples. We use IR images taken for a set of poly-Si wafers with the spatial resolution of roughly 20 microns. The raw PL intensities were subject to several post-processing steps, including averaging, noise removal using a 2-D Wiener filter, and a conversion between the PL rate and the estimated local electron density. Then the spatial distributions of NR recombination rates were predicted. These rates averaged over the whole sample and the measured minority lifetimes for the same Si wafers show negative correlation.
Sio, H, Phang, S, Trupke, T et al 2014, ‘An accurate method for calibrating photoluminescence-based lifetime images on multi-crystalline silicon wafers’, Solar Energy Materials and Solar Cells, vol. 131, pp. 77-84.
Uchechi Anyanwu, Christian Harris, Andrey Semichaevsky, ‘Carrier transport in polycrystalline silicon at high optical injection: transient photoconductance vs. numerical modeling,’ 44th IEEE-PVSC, Washington, DC, June 26, 2017.
Funder Acknowledgement(s): This work was supported through the NSF HRD HBCU-UP /RIA grant 1505377; Images were acquired by Mr. Logan Rowe at the Talbot Lab, UIUC and kindly provided to us
Faculty Advisor: None Listed,