Evidence for efficient passivation of vertical silicon nanowires by anodic aluminum oxide

We report on evaluation of effective carrier lifetimes of Si nanowires, which were selectively grown inside nanochannels of anodic aluminum oxide template using gas source molecule beam epitaxy. The carrier lifetime measurements were conducted under different injection level of irradiated photons at wavelength of 349 nm. It was found that anodic aluminum oxide template functioned not only as a mechanical guide of Si nanowires but also as an efficient passivation material. The effective carrier lifetime increased from 39 to 65.8 μs upon postdeposition anneal of 400 °C. Furthermore, thermal treatment at 650 °C could enhance the excited carriers to diffuse inside Si substrate and yielded a promising effective carrier lifetime of 152 μs. The Si nanowires embedded with anodic aluminum oxide templates are proved to be as potential candidate for fabrication of high efficiency solar cells.