Ultrathin SiO2/Al2O3 passivation for silicon heterojunctions using rapid thermal annealing

In this manuscript we study the surface passivation properties of ultrathin Al 2 O 3 in silicon heterojunctions. The Al 2 O 3 layer needs to be thin enough (<1.2nm) to enable carrier collection through the passivation layer. Previous work on Al 2 O 3 shows that thicknesses below 10nm do not provi...

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Published in2020 47th IEEE Photovoltaic Specialists Conference (PVSC) pp. 2104 - 2108
Main Authors Kim, Sangpyeong, Augusto, Andre, Bowden, Stuart G., Honsbeg, Christiana B.
Format Conference Proceeding
LanguageEnglish
Published IEEE 14.06.2020
Subjects
Al2O3 passivation
Aluminum oxide
Chemicals
Hydrogen
Passivation
Rapid thermal annealing
Silicon
SiO2 inter layer
Temperature measurement
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Summary:In this manuscript we study the surface passivation properties of ultrathin Al 2 O 3 in silicon heterojunctions. The Al 2 O 3 layer needs to be thin enough (<1.2nm) to enable carrier collection through the passivation layer. Previous work on Al 2 O 3 shows that thicknesses below 10nm do not provide adequate surface passivation. In this work, we combine 0.8 nm of Al 2 O 3 with 1nm of SiO 2 to improve the passivation properties of the thin Al 2 O 3 . The SiO 2 helps to improve the chemical passivation by increasing the storage capacity of hydrogen with Al 2 O 3 , and the overall negative fixed charge of the SiO 2 /Al 2 O 3 stack. Additionally, we have optimized the rapid thermal annealing in forming gas environment to activate the Al 2 O 3 in the SiO 2 /Al 2 O 3 stack. To further increase the hydrogen in the films we deposited n-a-Si:H film before the annealing step. Effective minority-carrier lifetimes of 5 ms and implied open-circuit voltages of 723 mV were accomplished.
DOI:10.1109/PVSC45281.2020.9300895