Spontaneous growth of III-nitride nanowires on Si by molecular beam epitaxy

In this paper, we report on the catalyst-free growth and the optoelectronic properties of GaN and InN nanowires (NWs) grown on Si(1 1 1) substrates by nitrogen RF plasma source molecular beam epitaxy (RF-MBE) without the use of intermediate GaN or AlN buffer layer. The growth conditions were optimized in order to fabricate well-aligned, stress-free single crystalline nanowires. In both cases, the III-nitride NWs were generated from the lattice mismatch strain of the materials on Si and the high surface energy of their nitrogen stabilized surfaces. Both PL and Raman spectroscopy revealed that the NWs were fully relaxed. XRD results further assert the single crystallinity of the nanowires.