InGaN Platelets: Synthesis and Applications toward Green and Red Light-Emitting Diodes

In this work, we present a method to synthesize arrays of hexagonal InGaN submicrometer platelets with a top c-plane area having an extension of a few hundred nanometers by selective area metal-organic vapor-phase epitaxy. The InGaN platelets were made by in situ annealing of InGaN pyramids, whereby InGaN from the pyramid apex was thermally etched away, leaving a c-plane surface, while the inclined {101̅1} planes of the pyramids were intact. The as-formed c-planes, which are rough with islands of a few tens of nanometers, can be flattened with InGaN regrowth, showing single bilayer steps and high-quality optical properties (full width at half-maximum of photoluminescence at room temperature: 107 meV for In_0.09Ga_0.91N and 151 meV for In_0.18Ga_0.82N). Such platelets offer surfaces having relaxed lattice constants, thus enabling shifting the quantum well emission from blue (as when grown on GaN) to green and red. For single InGaN quantum wells grown on the c-plane of such InGaN platelets, a sharp interface between the quantum well and the barriers was observed. The emission energy from the quantum well, grown under the same conditions, was shifted from 2.17 eV on In_0.09Ga_0.91N platelets to 1.95 eV on In_0.18Ga_0.82N platelets as a result of a thicker quantum well and a reduced indium pulling effect on In_0.18Ga_0.82N platelets. On the basis of this method, prototype light-emitting diodes were demonstrated with green emission on In_0.09Ga_0.91N platelets and red emission on In_0.18Ga_0.82N platelets.