Selective area growth of high-density GaN nanowire arrays on Si(111) using thin AlN seeding layers

Selective area growth (SAG) of high-density (2.5×109cm−2) GaN nanowires (NWs) on Si(111) substrate by plasma-assisted molecular beam epitaxy is presented. The effects of morphology and thickness of the AlN seeding layer on the quality of SAG GaN NWs are investigated. A thin AlN seeding layer of 30nm thick with a surface roughness of less than 0.5nm is suitable for high quality SAG GaN NWs growth. High-density AlN nanopedestal arrays used as seeds for SAG GaN NWs are fabricated from thin AlN seeding layers using soft nanoimprint lithography. By adjusting the growth temperature and Ga/N flux ratio, hexagonal shaped SAG GaN NWs are realized. The quality of SAG GaN NWs is evaluated by low temperature photoluminescence (PL) measurements. Three major groups of PL peaks at 3.47, 3.45, and 3.41eV are identified. The peak at 3.471eV is related to the neutral donor-bound exciton emission, and the 3.41eV broadband emission is attributed to stacking faults or structural defects. The 3.45eV peak is identified as the emission due to exciton recombination at polar inversion domain boundaries of NWs. •Systematic study conditions of selective area growth of GaN nanowires on Si(111).•Thin AlN seeding layer required for GaN nanowire growth is optimized.•The density of SAG GaN nanowires achieved is the highest (2E9cm−2).•Origin of major photoluminescence emission peaks of nanowires is identified.