Near-Infrared Photodetection of n-Type β-FeSi ²/Intrinsic Si/p-Type Si Heterojunctions at Low Temperatures

n-Type β-FeSi ₂/intrinsic Si/p-type Si heterojunction photodiodes were fabricated by facing-targets direct-current sputtering, and their infrared photodetection properties were studied at low temperatures. The rectification current ratio at bias voltages of ±1 V and the ratio of the photocurrent to the dark leakage current were dramatically enhanced with a decrease in temperature. The specific detectivities at 300 and 50 K were estimated to be 3:8 × 10 ⁹ and 8:9 × 10 ¹¹ cmHz ^1/2W ^-1, respectively. The enhanced detectivity upon cooling is attributed to the marked reduction in the dark leakage current. The insertion of the thin intrinsic Si layer slightly contributed to the suppression of the leakage current and the detectivity improvement. It was demonstrated that β-FeSi ² is a potential material for Si-compatible near-infrared photodetectors.