Preparation of n-Type $\beta $-FeSi$_{2}$/p-Type Si Heterojunctions for Near-Infrared Photodetectors by Pulsed Laser Deposition

Semiconducting $\beta $-FeSi$_{2}$ has attracted much attention owing to its attractive properties. $\beta $-FeSi$_{2}$ thin films have been fabricated by various methods. On the other hand, there have been few researches employing pulsed laser deposition (PLD), although it appears to be suitable for growing $\beta $-FeSi$_{2}$ films due to the following features: i) in order to suppress the diffusion of Fe atoms into Si substrates, deposition at a low substrate-temperature is preferable. PLD makes possible low temperature growth due to highly energetic species; ii) the chemical composition between the target and film is hardly changed in PLD. By using a sintered FeSi$_{2}$ target, $\beta $-FeSi$_{2}$ films expected to be as-grown on Si. In this study, $\beta $-FeSi$_{2}$ films were grown on Si(111) substrates at a substrate-temperature of 600 \r{ }C by PLD without post-annealing. The epitaxial relationships between the $\beta $-FeSi$_{2}$ film and Si(111) substrate were examined by X-ray diffraction (XRD). Several types of crystalline orientations co-existed in the film. The $\beta $-FeSi$_{2}$ film exhibited n-type conduction without doping, which might be due to Co and Ni impurities in the target that act as a donor in $\beta $-FeSi$_{2}$. Dark $I-V$ characteristics of the heterojunction showed a rectifying behavior. The photocurrent for irradiation with a 1.31-$\mu $m laser was low.