Large-area GaN n-core/p-shell arrays fabricated using top-down etching and selective epitaxial overgrowth

We present large-area, vertically aligned GaN n-core and p-shell structures on silicon substrates. The GaN pillars were formed by inductively coupled plasma etching of lithographically patterned n-GaN epitaxial layer. Mg-doped p-GaN shells were formed using selective overgrowth by halide vapor phase epitaxy. The diameter of the cores ranged from 250 nm to 10 mu m with varying pitch. The p-shells formed truncated hexagonal pyramids with {1 (1) over bar 01} side-facets. Room-temperature photoluminescence and Raman scattering measurements indicate strain-relaxation in the etched pillars and shells. Cross-sectional transmission electron microscopy revealed dislocation bending by 90 degrees at the core-shell interface and reduction in their density in the shells. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769376]