Structural and Optical Properties of InN Nanowires Formed on Si(111)

We report the structural and optical properties of InN nanowires (NWs) formed on p-type Si(111) substrates using a plasma-assisted molecular-beam epitaxy. The InN NWs were formed on a Si(111) substrate using a new growth method, the indium (In) pre-deposition (InPD) method, in which In droplets are initially formed by supplying only In flux to the substrate, where they work as nucleation sites for the formation of subsequent InN NWs. Field-emission scanning-electron microscopy images show that the InN NWs have symmetric shapes along the vertical direction. In addition, most of the InN NWs were unidirectionally grown in the direction perpendicular to the substrate. Strong and narrow peaks corresponding to InN(0002) can be clearly observed in the double crystal X-ray diffraction rocking curves of the NW samples. In the transmission electron microscopy images of the InN NWs, stacking faults, typically observed in Si-based III-nitride semiconductors, are rarely observed. A strong free-exciton peak was observed from the InN NWs at the wavelength of 1297 nm with a narrow linewidth at room temperature. Structural and optical characterizations of the NW samples indicate that highly crystalline InN NWs were formed on Si(111) using the new InPD growth method.