Enhancing Hot\nCarrier Photoelectric Efficiency through\nthe Boosted Collection of Hot Holes via Au/ZrO<sub>2</sub>/Si Tunneling\nJunctions

Metallic nanoparticles can generate\nphotoexcited hot carriers on\nthe femtosecond scale under light excitation, which holds immense\nsignificance for applications such as optical communication and ultrafast\nimaging. In this study, a tunnelling junction structure with ZrO<sub>2</sub> as the dielectric layer is designed and fabricated to achieve\nefficient hot hole collection between Au nanoparticles and P-type\nSi. Through characterizations of photoconductive atomic force microscopy,\nthe electrical transition from an ohmic contact to a tunneling junction\nis confirmed, and the transfer pathway of Au hot holes to P-type Si\nupon 520 nm excitation is clearly observed. The impact of the tunneling\nstructure on device performance is investigated through the fabrication\nof Si/ZrO<sub>2</sub>/Au/TiO<sub>2</sub> photodiodes. The performance\ntests show that hot hole collection by the tunneling effect significantly\nenhances a range of parameters, e.g., external quantum efficiency\nby 250%. Noticeably, the external quantum efficiency attributed to\nphotogenerated hot carriers under 520 nm excitation is estimated to\nexceed 2.5%. Moreover, the transient photoresponse of the photodiodes\nis examined with a typical rising time of less than 20 ns.