High-Efficiency Silicon Nanowire Array Near Infrared Photodetectors via Length Control and SiO_x Surface Passivation

Silicon (Si) nanowire (NW) array is a promising light-trapping platform due to the strong interaction between light and nanostructure. A photodetector benefits from the improved optical absorption in the Si NW array. Although the optical absorption increases with the NW length, the large NW length is not always preferable owing to the large surface area. Herein, the systematic study on the Si NW array photodetectors with varied NW lengths is investigated. It is revealed that the photodetectors with 1 µm length provide a highest responsivity of 0.65 A W⁻¹ and a specific detectivity of 1.40 × 10⁹ cm Hz^1/2 W⁻¹ at the wavelength of 1000 nm, including the dark current of 54 µA at 1 V. In addition, the silicon oxide (SiO_x) surface passivation is introduced to induce the high photogain. As a result, the responsivity is improved by 13 times (0.55 A W⁻¹) at 1100 nm. This work proposes high-efficiency Si NW array photodetectors by the NW array length control and the SiO_x surface passivation.