Growth of high-In-content InAlN nanocolumns on Si (1 1 1) by RF-plasma-assisted molecular-beam epitaxy

InxAl1−xN nanocolumns (xIn=0.73–1.00) of c-axis orientation were successfully self-organized on Si (1 1 1) substrates by RF-plasma-assisted molecular-beam epitaxy (RF-MBE). The height, diameter and density of nanocolumns were 0.7–1.1 μm, 40–130 nm, and 0.7–3.0×1010 cm−2, respectively. With increasing In composition from 0.73 to 1.00, the room-temperature photoluminescence (RT-PL) peak wavelengths shifted from 1.06 to 1.87 μm. AlN nanocolumns (when xIn=0) were also fabricated, and RT-PL was observed with a peak energy of 5.85 eV.