Monolithic integration of four‐colour InGaN‐based nanocolumn LEDs

The monolithic integration of four‐colour indium gallium nitride (InGaN)‐based nanocolumn light‐emitting diodes (LEDs) is demonstrated. In the integrated nanocolumn LED unit, blue‐, sky‐blue‐, green‐ and yellow‐emitting micro‐LEDs (LEDs 1–4) with a 65 μm diameter circular indium tin oxide emission window were arrayed in a 2 × 2 square lattice with a lattice constant of 190 μm. LEDs 1–4 consisted of nanocolumn arrays arranged in a triangular lattice with a lattice constant of 300 nm and their nanocolumn diameters at the position of the InGaN/gallium nitride (GaN) multiple quantum wells (MQWs) were 119, 145, 188 and 231 nm, respectively. The increase in nanocolumn diameter from LED 1 to LED 4 resulted in increasing emission peak wavelengths, which were 465, 489, 510 and 570 nm for LEDs 1–4, respectively. On the same substrate, a red‐emitting micro‐LED was prepared, in which the nanocolumn diameter was increased to 260 nm by using a 350 nm‐lattice‐constant nanocolumn array. A combination of different lattice constants in an integrated LED unit is expected to contribute to the achievement of red–green–blue–yellow (RGBY)‐colour‐integrated nanocolumn LEDs.