High-performance broadband photoresponse of self-powered Mg₂Si/Si photodetectors

Infrared optoelectronic devices are capable of operating in harsh environments with outstanding confidentiality and reliability. Nevertheless, suffering from the large band gap value, most semiconductor materials are difficult to detect infrared light signals. Here, Mg₂Si/Si heterojunction photodetectors (PDs), which possess the advantages of low-cost, easy process, environmental friendliness, and compatibility with silicon CMOS technology, have been reported with a broadband spectral response as tested from 532 to 1550 nm under zero-bias. When the incident light wavelength is 808 nm, the Mg₂Si/Si photodetector (PD) has a responsivity of 1.04 A W^-1and a specific detectivity of 1.51 × 10¹²Jones. Furthermore, we find that the Ag nanoparticles (Ag_NPs) assembled on the Mg₂Si layer can greatly improve the performance of the Mg₂Si/Si PD. The responsivity and specific detectivity of Mg₂Si/Si device with Ag_NPs under 808 nm illumination are 2.55 A W^-1and 2.60 × 10¹²Jones, respectively. These excellent photodetection performances can be attributed to the high-quality of our grown Mg₂Si material and the strong built-in electric field effect in the heterojunction, which can be further enhanced by the local surface plasmon effect and local electromagnetic field induced by Ag_NPs. Our study would provide significant guidance for the development of new self-powered infrared PDs based on silicon materials.