Non-edge-triggered inversion from Ga polarity to N polarity of c-GaN domains on an SiO₂ mask during epitaxial lateral overgrowth

It was previously reported that N-polar c-GaN domains nucleated in window openings on c-plane sapphire were inverted to Ga-polar domains at the edge of an SiO₂ mask during epitaxial lateral overgrowth, but it was asserted that polarity inversion of N-polar GaN domains could not occur beyond the edge of the SiO₂ mask. However, that assertion was demonstrated only in the case of a-facet-exposed GaN. It is reported here that polarity inversion from Ga polarity to N polarity of m-facet-exposed c-GaN domains occurred during epitaxial lateral overgrowth on the flat region beyond the edge of a circular-patterned SiO₂ mask. An increased flow rate of NH₃ during the epitaxial lateral overgrowth is thought to induce this type of non-edge-triggered polarity inversion. Further investigation reveals that non-edge-triggered polarity inversion is also possible when the a facet is exposed at the lateral growth front of Ga-polar GaN domains.