title: Ge nanopillar solar cells epitaxially grown by metalorganic chemical vapor deposition.
abstract: Radial junction solar cells with vertically aligned wire arrays have been widely studied to improve the power conversion efficiency. In this work, we report the first Ge nanopillar solar cell. Nanopillar arrays are selectively patterned on p-type Ge (100) substrates using nanosphere lithography and deep reactive ion etching processes. Nanoscale radial and planar junctions are realized by an n-type Ge emitter layer which is epitaxially grown by MOCVD using isobutylgermane. In situ epitaxial surface passivation is employed using an InGaP layer to avoid high surface recombination rates and Fermi level pinning. High quality n-ohmic contact is realized by protecting the top contact area during the nanopillar patterning. The short circuit current density and the power conversion efficiency of the Ge nanopillar solar cell are demonstrated to be improved up to 18 and 30%, respectively, compared to those of the Ge solar cell with a planar surface.
authors.affiliation: Department of Electrical and Computer Engineering, Ajou University, Suwon 16499, Korea.|Korea Advanced Nano Fab Center, Suwon 16229, Korea.
authors.forename: Youngjo
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Department of Electrical and Computer Engineering, Ajou University, Suwon 16499, Korea.|Department of Physics, Hanoi National University of Education, Hanoi 100000, Vietnam.
authors.forename: Nguyen Dinh
authors.initials: ND
authors.lastname: Lam
authors.affiliation: Department of Electrical and Computer Engineering, Ajou University, Suwon 16499, Korea.|Korea Advanced Nano Fab Center, Suwon 16229, Korea.
authors.forename: Kangho
authors.initials: K
authors.lastname: Kim
authors.affiliation: Korea Advanced Nano Fab Center, Suwon 16229, Korea.
authors.forename: Won-Kyu
authors.initials: WK
authors.lastname: Park
authors.affiliation: Department of Electrical and Computer Engineering, Ajou University, Suwon 16499, Korea.
authors.forename: Jaejin
authors.initials: J
authors.lastname: Lee