Study of hydrogenated AlN as an anti-reflective coating and for the effective surface passivation of silicon

• Published in: Physica status solidi. PSS-RRL. Rapid research letters 2013-07, Vol.7 (7), p.457-460
• Main Authors: Krugel, Georg, Sharma, Aashish, Wolke, Winfried, Rentsch, Jochen, Preu, Ralf
• Format: Article
• Language: English
• Subjects: AlN; Aluminum; anti-reflective coatings; Hydrogenation; passivation; photovoltaics; Protective coatings; Silicon; Surface roughness
• ISSN: 1862-6254; 1862-6270
• DOI: 10.1002/pssr.201307153

Stacks of aluminum oxide and silicon nitride are frequently used in silicon photovoltaics. In this Letter, we demonstrate that hydrogenated aluminum nitride can be an alternative to this dual‐layer stack. Deposited on 1 Ω cm p‐type FZ silicon, very low effective surface recombination velocities of 8 cm/s could be reached after firing at 820 °C. This excellent passivation is traced back to a high density of fixed charges at the interface of approximately –1 × 1012 cm–2 and a very low interface defect density below 5 × 1010 eV–1 cm–2. Furthermore, spectral ellipsometry measurements reveal that these aluminum nitride layers have ideal optical properties for use as anti‐reflective coatings. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) The passivation of the front and rear surface of a solar cell is a key feature to reach higher efficiencies. The authors show that sputtered AlN:H can be used as a passivation layer. Excellent passivation with lifetimes exceeding 1 ms is presented. This is traced back to a very low defect density and a high density of fixed charges at the interface to silicon. Furthermore, interesting optical properties are shown for these layers which make them an ideal material for a combined passivation layer and anti‐reflective coating.