Photoluminescence Excitation Spectroscopy of p-GaAs Surfaces and AlGaAs/GaAs Interfaces Supported by Numerical Modeling
Kyle H. Montgomery*, Dionisis Berdebes*, Jayprakash Bhosale, Jerry M. Woodall, and Mark S. Lundstrom
*contributed equally to this work
38th IEEE Photovoltaic Specialists Conference, Seattle, WA, 2012.
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Photoluminescence excitation spectroscopy (PLE) can be a very useful in-line metrology tool for photovoltaic manufacturing of III-V and chalcogenide-based, direct gap solar cells. We report on the experiment and numerical modeling of PLE measurements on GaAs–based test structures. Strong suppression of the band edge photoluminescence (PL) intensity is observed in bare, unpassivated GaAs samples, compared to an AlGaAs/GaAs double heterostructures (DH). Similarly, an observed reduction of PL intensity of the unpassivated samples with increasing excitation energy is associated with surface defects. A numerical drift-diffusion model is developed and two frameworks to describe the surface quality are studied, one involving the surface recombination velocity and one including a single trap level. For lightly-doped samples, where the effect of interface trap charging becomes important, the two simulation approaches lead to different spectroscopic response. For the examined samples, an estimated trap density of NT~1013 /cm2 is deduced.
photoluminescence, photovoltaic cells, gallium arsenide, charge carrier lifetime, numerical models.
K. H. Montgomery, D. Berdebes, J. Bhosale, J. M. Woodall, and M. S. Lundstrom, “Photoluminescence excitation spectroscopy of p-GaAs surfaces and AlGaAs/GaAs interfaces supported by numerical modeling,” presented at the 38th IEEE Photovoltaic Specialists Conference (PVSC), Austin, TX, 2012, pp. 000422-000426.