Monolithic multiple colour emission from InGaN grown on patterned non-polar GaN

A novel overgrowth approach has been developed in order to create a multiple-facet structure consisting of only non-polar and semi-polar GaN facets without involving any c-plane facets, allowing the major drawbacks of utilising c-plane GaN for the growth of III-nitride optoelectronics to be eliminated. Such a multiple-facet structure can be achieved by means of overgrowth on nonpolar GaN micro-rod arrays on r-plane sapphire. InGaN multiple quantum wells (MQWs) are then grown on the multiple-facet templates. Due to the different efficiencies of indium incorporation on non-polar and semi-polar GaN facets, multiple-colour InGaN/GaN MQWs have been obtained. Photoluminescence (PL) measurements have demonstrated that the multiple-colour emissions with a tunable intensity ratio of different wavelength emissions can be achieved simply through controlling the overgrowth conditions. Detailed cathodoluminescence measurements and excitationpower dependent PL measurements have been performed, further validating the approach of employing the multiple facet templates for the growth of multiple colour InGaN/GaN MQWs. It is worth highlighting that the approach potentially paves the way for the growth of monolithic phosphor-free white emitters in the future.