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Quantifying Bulk and Surface Recombination in CdSeTe Absorbers by Modeling Terahertz and Photoluminescence Decays
Conference proceeding

Quantifying Bulk and Surface Recombination in CdSeTe Absorbers by Modeling Terahertz and Photoluminescence Decays

Gregory A Manoukian, Calvin Fai, Deborah L McGott, Finley R Shapiro, Matthew O Reese, Charles J Hages and Jason B Baxter
2023 IEEE 50th Photovoltaic Specialists Conference (PVSC), pp 1-1
11 Jun 2023
DOI: https://doi.org/10.1109/PVSC48320.2023.10359677

Abstract

II-VI semiconductor materials Photoluminescence Radiative recombination Semiconductor device modeling Spectroscopy Surface waves
We demonstrate a technique for estimating critical recombination parameters Shockley-Read-Hall lifetime (τSRH) and front and back surface recombination velocities (SF and SB) in Cd(Se)Te. We evaluated uniform single heterostructures of glass/Al2O3/CdSexTe1-x/air (x = 0 & 0.2) using time resolved terahertz spectroscopy (TRTS) and time resolved photoluminescence (TRPL) with variable excitation wavelengths and powers as well as front vs back-side illumination. The addition of TRTS to traditional TRPL enhances analysis by providing insight into the first nanoseconds after photoexcitaton when TRPL is dominated by redistribution of carriers. Data were fit using numerical simulations of the semiconductor and Poisson' equations with best-fit parameters determined by Bayesian inference. Our CdSe0.2Te0.8 films had τSRH ~50 ns, compared with ~26 ns for CdTe. τSRH values extracted from our model were approximately double those derived from multi-exponential fit of TRPL decays, which do not rigorously account for surface recombination. Se alloying also decreased SB from 2×105 to 6×103 cm/s. Upper limits of 104 and 103 cm/s were determined for SF for CdTe and CdSe0.2Te0.8, respectively. Precise determination of recombination velocity at the well-passivated Al2O3/ CdSexTe1-x interface was limited by the dominant bulk and/or back surface recombination in these films. This study was made on passivated heterostructures of absorber layers to for the primary purpose of evaluating new methods of parameter determination. Further development of the models toward full devices can lead to rapid correlation of changes in bulk lifetime and surface recombination rates with processing and could enable evaluation of effects of electric fields and other phenomena that cannot be captured using conventional approaches.

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