Tantalum oxide/silicon nitride: A negatively charged surface passivation stack for silicon solar cells
Date
2015
Authors
Wan, Yimao
Bullock, James
Cuevas, Andres
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American Institute of Physics (AIP)
Abstract
This letter reports effective passivation of crystalline silicon (c-Si) surfaces by thermal atomic layer deposited tantalum oxide (Ta<inf>2</inf>O<inf>5</inf>) underneath plasma enhanced chemical vapour deposited silicon nitride (SiN<inf>x</inf>). Cross-sectional transmission electron microscopy imaging shows an approximately 2 nm thick interfacial layer between Ta<inf>2</inf>O<inf>5</inf> and c-Si. Surface recombination velocities as low as 5.0 cm/s and 3.2 cm/s are attained on p-type 0.8 Ω·cm and n-type 1.0 Ω·cm c-Si wafers, respectively. Recombination current densities of 25 fA/cm2 and 68 fA/cm2 are measured on 150 Ω/sq boron-diffused p+ and 120 Ω/sq phosphorus-diffused n+ c-Si, respectively. Capacitance-voltage measurements reveal a negative fixed insulator charge density of -1.8 × 1012cm-2 for the Ta<inf>2</inf>O<inf>5</inf> film and -1.0 × 1012cm-2 for the Ta<inf>2</inf>O<inf>5</inf>/SiN<inf>x</inf> stack. The Ta<inf>2</inf>O<inf>5</inf>/SiN<inf>x</inf> stack is demonstrated to be an excellent candidate for surface passivation of high efficiency silicon solar cells.
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Applied Physics Letters
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Journal article
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