Surface morphology-dependent photoelectrochemical properties of one-dimensional Si nanostructure arrays prepared by chemical etching.

Maximizing the optical absorption of one-dimensional Si nanostructure arrays (1DSiNSAs) is desirable for excellent performance of 1DSiNSA-based optoelectronic devices. However, a quite large surface-to-volume ratio and enhanced surface roughness are usually produced by modulation of the morphology of the 1DSiNSAs prepared in a top-down method to improve their optical absorption. Surface recombination is mainly determined by the surface characteristics and significantly affects the photogenerated carrier collection. In this paper, we systematically investigated the photoelectrochemical characteristics of 1DSiNSAs with various morphologies prepared by the metal-assisted chemical etching of Si wafers. Our results show that the saturation photocurrent density and photoresponsivity of 1DSiNSAs first increased and then gradually decreased with an increasing etching time, while the reflection spectrum was gradually suppressed to the measurable minimum. To identify the behaviors of the photoresponsivity and optical absorption of the various 1DSiNSAs, we analyzed the morphology, structure, and minority-carrier lifetime. Additionally, device physics simulations were used to confirm the significance of surface recombination. We proposed that future directions for the design of nanostructure-based optoelectronic devices should include not only strong optical absorption but also low surface carrier recombination. High-performance devices could be obtained only by balancing the requirements for light absorption and photogenerated carrier collection.