Surface Passivation Properties of } Thin Film on n-Type Crystalline Si

Atomic layer deposited hafnium oxide is shown to provide good surface passivation of low resistivity, n-type crystalline Si wafers after a low temperature anneal. The surface passivation is related to a fixed negative charge, as well as an excellent interface with the crystalline Si wafer. In this p...

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Bibliographic Details
Published in:IEEE journal of photovoltaics 2017-03, Vol.7 (2), p.479-485
Main Authors: Xuemei Cheng, Repo, Paivikki, Halvard, Haug, Perros, Alexander Pyymaki, Marstein, Erik Stensrud, Di Sabatino, Marisa, Savin, Hele
Format: Article
Language:English
Subjects:
Annealing
Atomic layer deposition (ALD)
defect density
fixed charges
Hafnium compounds
hafnium oxide (HfO<sub xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">2 )
Passivation
photovoltaic cells
Silicon
silicon surface passivation
Temperature measurement
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Summary:Atomic layer deposited hafnium oxide is shown to provide good surface passivation of low resistivity, n-type crystalline Si wafers after a low temperature anneal. The surface passivation is related to a fixed negative charge, as well as an excellent interface with the crystalline Si wafer. In this paper, the influence of four deposition parameters on the HfO 2 passivation properties, namely precleaning, precursors, deposition temperature, and postannealing temperature, is discussed. Minority carrier lifetimes of 1.9 ms (surface recombination velocity (SRV) 7.7 cm/s) on float zone n-type wafers and 1.7 ms (SRV 11 cm/s) on Czochralski n-type wafers, under optimized deposition conditions and a postannealing process, have been measured. A significant improvement of the surface passivation is observed after 100 h light soaking, resulting in a carrier lifetime of 2.5 ms. Fitting of the results by a two-defect charge trapping/detrapping model indicates that additional light-induced negative charges enhance the field effect passivation, which is also consistent with the experimental results. Due to its high refractive index and the obtained good surface passivation of Si wafers, HfO 2 has a great potential as a surface passivation material, e.g., in the fabrication of high-efficiency Si solar cells.
ISSN:2156-3381
2156-3403
DOI:10.1109/JPHOTOV.2016.2645399