文摘
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.