Enhanced performance of a Mg2Si/Si heterojunction photodetector grown with the assistance of nanostructures

Abstract

As a non-toxic and non-polluting semiconductor material, Mg₂Si/Si has great potential for application in the field of visible and near-infrared photo detection due to its excellent physical properties. In this work, Mg₂Si/Si thin films were prepared by magnetron sputtering of Mg film on Si substrate followed by an annealing process. The effects of annealing temperature and annealing time on the growth of Mg₂Si/Si thin film were studied, and large-area high-quality Mg₂Si/Si thin film was prepared at an annealing temperature of 420 °C and an annealing time of 8 h. To improve the quality of Mg₂Si/Si thin film and the performance of the Mg₂Si/Si heterojunction photodetector, nanostructures were fabricated in the surface of the Si substrate by using an anodic aluminum oxide (AAO) mask and a plasma etching process. The nanostructures enable the Mg film and Si substrate to have an increased contact area and facilitate the solid-phase reaction between Mg and Si to grow Mg₂Si/Si film. For the visible and near-infrared bands, the integration of nanostructures provides the photodetectors with a 173–402% improvement in responsivity and a 111–281% improvement in specific detectivity compared to normal Mg₂Si/Si heterojunction devices. The maximum responsivity of the device is 183 mA W⁻¹, and the specific detectivity is enhanced to 9.43 × 10⁹ Jones at 1064 nm. This work provides a new approach for the development and application of Si-based Mg₂Si/Si film and Mg₂Si/Si heterojunction photodetectors with high performance.