Direct radiative recombination in the Se-terminated nanoscale Si porous structure

We prepared vertical porous silicon nanowire (SiNW) arrays using the silver-assisted electroless etching method. The post-selenization treatment was carried out to passivate the surface of the nanostructure with Se-related bonds. Besides the great enhancement of the photoluminescence (PL) intensity and stability, the slow red emission band from the untreated porous SiNWs disappears and the new PL bands blue-shift to the higher energy, with the recombination rate more than three orders of magnitudes faster than that of the red emission band. The lifetime of 0.49 and 2.68 ns are attributed to the recombination in the Si nanostructures passivated with Sisingle bondSe, and Sisingle bondSesingle bondO bonds, respectively. The fast recombination rates indicate that surface modification induced by selenization treatment could lead to the direct radiative recombination of Si nanostructure. Furthermore, a broad near-infrared emission band located at around ∼1300 nm is also observed. These results are thought useful in the band gap engineering of Si.