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Hydrogenation Mechanisms of Poly‐Si/SiO x Passivating Contacts by Different Capping Layers
Author(s) -
Truong Thien N.,
Yan Di,
Chen Wenhao,
Tebyetekerwa Mike,
Young Matthew,
Al-Jassim Mowafak,
Cuevas Andres,
Macdonald Daniel,
Nguyen Hieu T.
Publication year - 2020
Publication title -
solar rrl
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.544
H-Index - 37
ISSN - 2367-198X
DOI - 10.1002/solr.201900476
Subject(s) - passivation , dangling bond , materials science , analytical chemistry (journal) , plasma enhanced chemical vapor deposition , annealing (glass) , amorphous solid , chemical vapor deposition , atomic layer deposition , silicon , electrical resistivity and conductivity , silicon nitride , hydrogen , photoluminescence , nanotechnology , thin film , layer (electronics) , optoelectronics , chemistry , crystallography , composite material , engineering , organic chemistry , chromatography , electrical engineering
Herein, posttreatment techniques of phosphorus‐doped poly‐Si/SiO x passivating contacts, including forming gas annealing (FGA), atomic layer deposition (ALD) of hydrogenated aluminum oxide (AlO x :H), and plasma‐enhanced chemical vapor deposition (PECVD) of hydrogenated silicon nitride (SiN x :H), are investigated and compared in terms of their application to silicon solar cells. A simple FGA posttreatment produces a significant increase in the implied open circuit voltage (iV oc ) and the effective minority‐carrier lifetime ( τ eff ) of high‐resistivity crystalline Si (c‐Si) samples, whereas low‐resistivity samples show a minimal change. Treatment by means of AlO x :H and/or SiN x :H followed by postdeposition FGA results in a universal increase in τ eff and iV oc for all substrate resistivities (as high as 12.5 ms and 728 mV for 100 Ω cm and 5.4 ms and 727 mV for 2 Ω cm n‐type c‐Si substrates). In addition, both the FGA and AlO x :H + FGA techniques can inject sufficient hydrogen into the samples to passivate defects at the SiO x /c‐Si and poly‐Si/SiO x interfaces. However, this hydrogen concentration is insufficient to neutralize both the nonradiative defects inside the poly‐Si films and dangling bonds associated with the amorphous Si phase present in them. The hydrogen injected by the SiN x :H + FGA technique can passivate both the interfaces and the defects and dangling bonds within the poly‐Si film. These results are confirmed by low‐temperature photoluminescence spectroscopy, Fourier transform infrared spectroscopy, and dynamic secondary‐ion mass spectrometry measurements.