Novel selective area growth (SAG) method for regularly arranged AlGaN nanocolumns using nanotemplates

We have demonstrated a novel selective area growth (SAG) method based on rf-plasma-assisted molecular beam epitaxy for AlGaN nanocolumns using nanotemplates. The nanotemplates, which were prepared on a metal-organic chemical vapor deposition-GaN template, consisted of a triangular lattice of nanopillars with a lattice constant from 200 to 400 nm. For nanopillars with a lattice constant of 400 nm, the gap width between adjacent pillars was varied from 30 to 130 nm. The well-controlled SAG of GaN nanocolumns was achieved on nanopillar arrays with gap widths of less than approximately 45 nm. The beam shadowing effect, which was induced in the high-density nanopillar arrays with small gaps, was a key mechanism in the SAG. This gap width condition for SAG was satisfied for lattice constants from 200 to 400 nm. Using the nanotemplate SAG technology, the SAG of AlGaN nanocolumn arrays was achieved for Al compositions of 0.13, 0.22, 0.43, and 1. Single-peak photoluminescence (PL) spectra of AlGaN were observed, whose wavelengths were close to the calculated bandgap wavelengths using the bandgaps of AlN (6.015 eV) and GaN (3.39 eV) and a bowing parameter of 0.98 eV.