Growth rate and indium incorporation during growth of InGaN/GaN quantum well structures in pyramidal micro-LED devices

Pyramidal micro-light emitting diodes (μLEDs) based on five InGaN/GaN quantum well (QW) pairs were synthesized via selective area growth in a metal-organic chemical vapor deposition system. Electroluminescence, optical microscopy, and cathodoluminescence (CL) were used to study the emission properties of the pyramidal μLEDs. The QW emission from the pyramidal structures reaches shorter wavelengths with increasing bias, which can be ascribed to the subsequent activation of InGaN QWs with increasing bandgaps. According to CL and plan-view scanning transmission electron microscopy, the longer emission wavelengths correlate spatially with increasing indium content associated with the pyramid ridges. Further imaging and elemental mapping of the QWs near the pyramid ridges reveal that adjacent QWs interface through a trench, situated precisely along the ridge between facets, wherein the QWs are thicker and the In content is enhanced. It is inferred that both parameters are induced by a higher growth rate in the trenches. The herein presented results provide a detailed view of how In incorporation and hence the emission properties are affected by the different growth rates that occur through geometrical variations in pyramidal μLEDs.