Mg ₂ Si/Si vertical heterojunction near-infrared photodetector

Abstract

Mg 2 Si, a narrow-bandgap semiconductor, excels in near-infrared (NIR) (700–1700 nm) light harvesting. However, Mg 2 Si-based NIR photodetectors (PDs) on silicon show limited response beyond 1100 nm. This study presents a high-performance Mg 2 Si/Si vertical heterojunction PD for NIR detection. We investigated the ITO/Mg 2 Si/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 × 10 9 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.