Mg2Si/Si Vertical Heterojunction Near-Infrared Photodetector

Mg2Si, a narrow-bandgap semiconductor, excels in near-infrared (NIR) (700–1700 nm) light harvesting. However, Mg2Si-based NIR photodetectors (PDs) on silicon show limited response beyond 1100 nm. This study presents a high-performance Mg2Si/Si vertical heterojunction PD for NIR detection. We investigated the ITO/Mg2Si/Si heterojunction device using a co-simulation framework that combines FDTD optical and CHARGE electrical models. The structure exhibits strong rectification, significantly reducing dark current. Photoelectrical characterization at 1064 nm demonstrated enhanced photocurrent under zero-bias, achieving a responsivity (R) of ≈230 mA/W. Optimal self-powered performance was observed at 1310 nm, with R ≈1.2 mA/W, specific detectivity (D*) ≈1×10⁹ Jones, a response time of 73.5 μs, and a 3 dB bandwidth of ≈3.1 kHz. Finally, a proof-of-concept optical communication system successfully transmitted ASCII-encoded data using 1310 nm NIR light, highlighting the device's potential for low-power NIR applications.