GaAs/Indium Tin Oxide/Si Bonding Junctions for III-V-on-Si Hybrid Multijunction Cells With Low Series Resistance

Naoteru Shigekawa,Takefumi Kamioka,Kenji Araki,Tomoya Hara,Tomoki Ogawa,Jianbo Liang,Masafumi Yamaguchi

doi:10.1109/jphotov.2018.2802203

Naoteru Shigekawa, Takefumi Kamioka + Show 5 more

https://doi.org/10.1109/jphotov.2018.2802203

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Effects of GaAs/indium tin oxide (ITO)/Si junctions on III-V-on-Si multijunction solar cells are examined by fabricating and characterizing InGaP/GaAs/ITO/Si triple-junction (3J) solar cells. The 3J cells are fabricated by evaporating ≈ 100-nmthick ITO films on the surfaces of Si bottom cells and bonding the InGaP/GaAs double-junction (2J) subcells and the ITO films using surface-activated bonding technologies at room temperature. The current-voltage characteristics of 3J cells with p + -GaAs/ITO/n + -Si and n + -GaAs/ITO/n + -Si junctions are compared with those of an InGaP/GaAs/Si 3J cell. The parasitic resistance of the respective 3J cells is estimated by analyzing their characteristics in the dark. We find that the 3J cell with an n + -GaAs/ITO/n + -Si junction shows the lowest parasitic resistance, which is the origin of its lowest differential resistance at the open-circuit voltage and highest fill factor. This means that n + -GaAs/ITO/n + -Si junctions are promising for improving the performances of III-V-on-Si hybrid multijunction cells. The spectral response characteristics of these cells indicate that the thickness of the ITO films must be optimized.

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