title: Macroporous p-GaP Photocathodes Prepared by Anodic Etching and Atomic Layer Deposition Doping.
abstract: P-type macroporous gallium phosphide (GaP) photoelectrodes have been prepared by anodic etching of an undoped, intrinsically n-type GaP(100) wafer and followed by drive-in doping with Zn from conformal ZnO films prepared by atomic layer deposition (ALD). Specifically, 30 nm ALD ZnO films were coated on GaP macroporous films and then annealed at T = 650 °C for various times to diffuse Zn in GaP. Under 100 mW cm(-2) white light illumination, the resulting Zn-doped macroporous GaP consistently exhibit strong cathodic photocurrent when measured in aqueous electrolyte containing methyl viologen. Wavelength-dependent photoresponse measurements of the Zn-doped macroporous GaP revealed enhanced collection efficiency at wavelengths longer than 460 nm, indicating that the ALD doping step rendered the entire material p-type and imparted the ability to sustain a strong internal electric field that preferentially drove photogenerated electrons to the GaP/electrolyte interface. Collectively, this work presents a doping strategy with a potentially high degree of controllability for high-aspect ratio III-V materials, where the ZnO ALD film is a practical dopant source for Zn.
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and §Program in Applied Physics, University of Michigan , 930 N. University, Ann Arbor, Michigan 48109-1055, United States.
authors.forename: Sudarat
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and §Program in Applied Physics, University of Michigan , 930 N. University, Ann Arbor, Michigan 48109-1055, United States.
authors.forename: Ashley R
authors.initials: AR
authors.lastname: Bielinski
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and §Program in Applied Physics, University of Michigan , 930 N. University, Ann Arbor, Michigan 48109-1055, United States.
authors.forename: Eli
authors.initials: E
authors.lastname: Fahrenkrug
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and §Program in Applied Physics, University of Michigan , 930 N. University, Ann Arbor, Michigan 48109-1055, United States.
authors.forename: Neil P
authors.initials: NP
authors.lastname: Dasgupta
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and §Program in Applied Physics, University of Michigan , 930 N. University, Ann Arbor, Michigan 48109-1055, United States.
authors.forename: Stephen
authors.initials: S
authors.lastname: Maldonado
keywords: III−V; atomic layer deposition; gallium phosphide; nanostructured; photoelectrochemistry