We present large-area, vertically-aligned GaN core-shell structures on silicon substrates. The GaN cores were formed by inductively coupled plasma etching of patterned n-type GaN epitaxial layer. The Mg-doped GaN shells were formed using selective overgrowth by halide vapor phase epitaxy. The diameter of the cores ranged from 250 nm to 10 um with varying pitch. The p-type shells formed truncated hexagonal pyramids with prismatic  side-facets. Room-temperature photoluminescence, and Raman scattering measurements indicated strain-relaxation in the etched cores and shells. Cross-sectional transmission electron microscopy revealed dislocation bending by 90 degrees in the shells, which led to their reduction in the overgrown shells.
Citation: Journal of Applied Physics
Pub Type: Journals
Core-shell, GaN, nanostructures, p-n junction, top-down