n-Type $\beta $-FeSi$_{2}$/p-Type Si Hererojuncion Photodiodes Fabricated by Facing Targets Direct-Current Sputtering

Semiconducting iron disilicide ($\beta $-Fesi$_{2})$ has been received much attention, since this material has several attractive characteristics. Specifically, it is a new candidate material for near-infrared (NIR) photodetectors for optical fiber communication because its optical band gap is optimum for operating at wavelengths of 1.3 and 1.55 $\mu$m. In this study, $\beta $-FeSi$_{2}$ thin films were epitaxially grown on Si(111) substrates by facing targets direct-current sputtering (FTDCS) at a substrate-temperature of 600$^{\circ}$C without post-annealing at a high temperature. In the dark and under illumination at a wavelength of 1.31$\mu$m, the photodiode performance was measured in the temperature range from 50 to 300 K. At a low temperature, the performances were remarkably improved as compared with those at 300 K. The $R_{0}A$ product and detectivity at 50 K were estimated to be 2.0 $\times$ 10$^{8} \quad \Omega $ cm$^{2}$ and 2.8 $\times$ 10$^{11}$cm$\cdot$Hz$^{1/2}$/W, respectively.