Yong-Qiang Yu, Lin-Bao Luo^*， Zhi-Feng Zhu, Biao Nie, Yu-Gang Zhang,  Long-Hui Zeng, Yan Zhang, Chun-Yan Wu, Li Wang, and Yang Jian^*

Abstract: Ag-doped  p-type ZnS nanoribbons (NRs) with  high hole concentration of 5.1×10¹⁸ cm^-3 and high carrier mobility of 154.0 cm²V^-2s^-1 were synthesized by using sliver sulfide (Ag₂S) as Ag source.  Excellent ohmic contact to p-ZnS NR  with specific contact resistivity as low as 5.6×10^-7 Ωcm² was achieved by using bilayer Cu(4nm)/Au electrode, which, according to the  depth profiling X-ray photoelectron spectroscopy (XPS) and Auger electron  spectroscopy (AES) analysis can help to form a thin Cu₂S interfacial  layer between the electrode.Based on the high quality ZnS  NRs and achievement on ohmic contact, p-n photodiodes has been constructed from the p-ZnS nanoribbon (NR)/n-Si  heterojunction with a response speed as high as ~ 48 μs (rise time). Furthermore,  the device also exhibits stable optoelectrical properties with high sensitivity  to UV-visible-NIR light and an enhancement of responsivities of 1.1×10³ AW^-1for 254 nm under a reverse  bias of 0.5 V. These  generality of the above results shows that the p-ZnS NR/n-Si  heterojunction will have potential applications in future high-performance  photodetectors.