GaN nanopillar arrays have been fabricated by inductively coupled plasma etching of GaN films using anodic aluminum oxide film as an etch mask. The average diameter and length of these pillars are 60–65nm and 350–400nm, respectively. Ultraviolet microphotoluminescence measurements indicate high photoluminescence intensity and stress relaxation in these GaN nanopillars as compared to the starting epitaxial GaN films. Evidence of good crystalline quality is also observed by micro-Raman measurements, wherein a redshift of the E2high mode from GaN nanopillars suggests partial relaxation of the compressive strain. In addition, breakdown of the polarization selection rules led to the appearance of symmetry-forbidden and quasipolar modes.

We demonstrate that GaN can selectively grow by metalorganic chemical vapor deposition into the pores and laterally over the nanoscale patterned SiO2 mask on a template of GaN∕AlN∕Si. The nanoporous SiO2 on GaN surface with pore diameter of approximately 65 nm and pore spacing of 110 nm was created by inductively coupled plasma etching using anodic aluminum oxide template as a mask. Cross-section transmission electron microscopy shows that the threading-dislocation density was largely reduced in this nanoepitaxial lateral overgrowth region. Dislocations parallel to the interface are the dominant type of dislocations in the overgrown layer of GaN. A large number of the threading dislocations were filtered by the nanoscale mask, which leads to the dramatic reduction of the threading dislocations during the growth within the nano-openings. More importantly, due to the nanoscale size of the mask area, the very fast coalescence and subsequent lateral overgrowth of GaN force the threading dislocations to bend to the basal plane within the first 50 nm of the film thickness. The structure of overgrown GaN is a truncated hexagonal pyramid which is covered with six {11¯01} side facets and (0001) top surface depending on the growth conditions.

Uniform and ordered ZnO nanowire arrays have been fabricated on the nanopatterned SiO2∕GaN substrate without metal catalysts using hydrothermal synthesis. The nanopatterns on SiO2∕GaN substrate with an average diameter of 65nm are produced by inductively coupled plasma etching using anodic alumina template as a mask, which provides nucleation sites for the vertical ZnO nanowires growth. High quality of the aligned uniform ZnO nanowire arrays grown on GaN substrate was confirmed by x-ray diffraction, transmission electron microscopy, and photoluminescence. This growth technique provides a cost-effective approach to fabricate ordered nanowire arrays with controlled size, which may benefit the nanowire device applications.

A site-control nucleation and growth approach for dense InGaN nanodots has been demonstrated on the surface of GaN using a nonlithographic nanopatterning technique by metal organic chemical vapor deposition. Shallow nanopore arrays with a depth of ∼15nm are created by inductively coupled plasma etching in the GaN surface using anodic aluminum oxide films as etch masks. The nanopores are found to be the preferential sites for the InGaN nanodot formation. Uniform InGaN nanodot arrays with a density as high as 1010∕cm2 as defined by the nanopores in GaN were observed on the surface. A strong photoluminescence (PL) emission peak near 2.8eV is observed from the InGaN nanodots. The temperature dependence of PL shows the enhanced carrier localization with higher activation energy in the InGaN nanodots when compared to the InGaN thin layer grown simultaneously on the nonpatterned GaN surface.