Near-infrared photodetection in n-type nanocrystalline FeSi ₂/p-type Si heterojunctions

n-Type nanocrystalline (NC) FeSi₂/p-type Si heterojunctions, which were prepared by pulsed laser deposition, were evaluated as a near infrared photodiode. The built-in potential was estimated to be approximately 1.1 eV from the capacitance-voltage measurement. These junctions showed a rectifying behavior accompanied by a large leakage current. The near infrared light detection performance was evaluated using a 1.33 μm laser in the temperature range of 77-300 K. At a reverse bias of -5 V, the detectivity was 5.5 × 10⁷ cm Hz^1/2 W^-1 at 300 K and it was dramatically enhanced to be 8.0 × 10¹⁰ cm Hz^1/2 W^-1 at 77 K. It was demonstrated that NC-FeSi₂ is a new potential material applicable to NIR photodetectors operating at low temperatures.