Surface charge transfer induced p-CdS nanoribbon/n-Si heterojunctions as fast-speed self-driven photodetectors

Abstract

Heterojunctions composed of single p-type CdS nanoribbons (NRs) and n-type silicon (Si) were successfully fabricated. The p-type CdS NRs were realized through a facile surface charge transfer doping approach. A typical as-fabricated p–n heterojuction exhibits excellent rectifying behavior with a rectification ratio up to ∼2 × 10³ within ±1.5 V, a low turn-on voltage of ∼0.5 V and a small ideality factor of 1.29. Furthermore, due to the strong photovoltaic effect, the heterojunction is found to be highly sensitive to visible light irradiation at zero bias voltage with a large I_light/I_dark ratio (2 × 10³), fast response speed (t_r = 26 μs and t_f = 112 μs), good reproducibility and long-term stability. The present work suggests great potential of such a heterojunction for future high-speed photodetector applications, and more importantly, signifying the feasibility of applying the surface charge transfer doping technique for constructing novel nano-optoelectronic devices.