N-type nanocrystalline FeSi ₂/intrinsic Si/p-type si heterojunction photodiodes fabricated by facing-target direct-current sputtering

n-Type nanocrystalline (NC) FeSi ₂/intrinsic (i) Si/p-type Si heterojunctions, which were prepared by facing-target direct current sputtering, were evaluated as near-infrared photodiodes, and the effects of thin i-Si layer insertion on diode performance were studied. Their junction capacitance and reverse leakage current were clearly reduced compared with those of n-type NC-FeSi ₂/p-type Si heterojunctions. The capacitance-voltage curve implied that the effects of interface states is relatively suppressed by i-Si insertion. The near-infrared light detection performance was investigated using a 1.33 μm laser in the temperature range of 77-300 K. The detectivities at 300 and 77 K were 1.9 × 10 ⁸ and 3.0 × 10 ¹¹ cmHz ^1/2W ^-1, respectively, at a negative bias of -5 V, which were markedly improved compared with that of p-n heterojunctions. This might be because the formation of interface states that act as trap centers for photocarriers is suppressed.