Lateral epitaxial overgrowth of nitrogen polar GaN on smooth nitrogen polar GaN templates by metalorganic chemical vapor deposition

Nitrogen (N)-polar GaN lateral epitaxial overgrowth (LEO), with a reduced dislocation density, is grown by metalorganic chemical vapor deposition on patterned, smooth N-polar templates. For LEO growth conditions identical to that of smooth N-polar GaN on sapphire, mask orientation dependent morphologies and faceting of the overgrowth regions are observed. N-polar LEO oriented along the 〈1-100〉 direction exhibit flat sidewall morphologies while LEO oriented along the 〈11-20〉 direction exhibit inclined sidewalls. A lateral to vertical growth ratio for the 〈1-100〉 and 〈11-20〉 oriented LEO was found to be ∼0.3 and 0.2, respectively. Transmission electron microscope observations reveal a reduction of dislocations of up to three orders of magnitude in the overgrowth regions from ∼10¹⁰ cm⁻² in the template. Additionally, dislocation bending likely initiated from interfacial tension between the N-polar GaN and SiO₂ mask is observed, resulting in a reduction of dislocation density to ∼10⁹ cm⁻² in the window region of re-growth.