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Formation of a Positive Fixed Charge at $c − Si (111) / a − {Si}_{3} N_{3.5} : H$ Interfaces

L. E. Hintzsche¹, C. M. Fang¹, M. Marsman¹, M. W. P. E. Lamers², A. W. Weeber², and G. Kresse¹

¹University of Vienna, Faculty of Physics and Center for Computational Materials Science, Sensengasse 8/12, A-1090 Vienna, Austria
²ECN Solar Energy, P.O. Box 1, 1755 ZG Petten, The Netherlands

Phys. Rev. Applied 3, 064005 – Published 11 June, 2015

DOI: https://doi.org/10.1103/PhysRevApplied.3.064005

Abstract

Modern electronic devices are unthinkable without the well-controlled formation of interfaces at heterostructures. These structures often involve at least one amorphous material. Modeling such interfaces poses a significant challenge, since a meaningful result can be expected only by using huge models or by drawing from many statistically independent samples. Here we report on the results of high-throughput calculations for interfaces between crystalline silicon ( $c − Si$ ) and amorphous silicon nitride ( $a − {Si}_{3} N_{3.5} : H$ ), which are omnipresent in commercially available solar cells. The findings reconcile only partly understood key features. At the interface, threefold-coordinated Si atoms are present. These are caused by the structural mismatch between the amorphous and crystalline parts. The local Fermi level of undoped $c − Si$ lies well below that of $a − Si N : H$ . To align the Fermi levels in the device, charge is transferred from the $a − Si N : H$ part to the $c − Si$ part resulting in an abundance of positively charged, threefold-coordinated Si atoms at the interface. This explains the existence of a positive, fixed charge at the interface that repels holes.

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References (29)

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Formation of a Positive Fixed Charge at $c − Si (111) / a − {Si}_{3} N_{3.5} : H$ Interfaces

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Formation of a Positive Fixed Charge at c−Si(111)/a−Si3N3.5:H Interfaces

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Article Text

References (29)

Formation of a Positive Fixed Charge at $c − Si (111) / a − {Si}_{3} N_{3.5} : H$ Interfaces