High efficiency n-Si/p-Cu₂O core-shell nanowires photodiode prepared by atomic layer deposition of Cu₂O on well-ordered Si nanowires array

A highly efficient n-Si/p-Cu₂O core-shell (C-S) nanowire (NW) photodiode was fabricated using Cu₂O grown by atomic layer deposition (ALD) on a well-ordered Si NW array. Ordered Si nanowires arrays were fabricated by nano-sphere lithography to pattern metal catalysts for the metal-assisted etching of silicon, resulting in a Si NW arrays with a good arrangement, smooth surface and small diameter distribution. The ALD-Cu₂O thin films were grown using a new non-fluorinated Cu precursor, bis(1-dimethylamino-2-methyl-2-butoxy)copper (C₁₄H₃₂N₂O₂Cu), and water vapor (H₂O) at 140°C. Transmission electron microscopy equipped with an energy dispersive spectrometer confirmed that p-Cu₂O thin films had been coated over arrayed Si NWs with a diameter of 150 nm (aspect ratio of ∼7.6). The C-S NW photodiode exhibited more sensitive photodetection performance under ultraviolet illumination as well as an enhanced photocurrent density in the forward biasing region than the planar structure diode. The superior performance of C-S NWs photodiode was explained by the lower reflectance of light and the effective carrier separation and collection originating from the C-S NWs structure. [Figure not available: see fulltext.]