Narrower Emission Spectra From Multicolor InGaN Quantum Wells Monolithically Integrated on Polyhedral-Shaped GaN Templates

InGaN-based quantum wells (QWs) integrated on arbitrary-shaped 3D GaN templates are promising light sources for ultra-high-resolution micro-LED displays. In this paper, we first demonstrate that the emissions from InGaN QWs on polyhedral-shaped GaN templates are broader than those from planar QWs. Microscopic observations by scanning electron microscopy and cathodoluminescence spectroscopy reveal that the broad emission is due to surface undulations formed during the crystal regrowth of the QW regions on the GaN templates. To suppress the formation of undulations, we subject 3D GaN templates to chemical mechanical polishing before the regrowth. This method successfully reduces the emission spectral width by $\sim$20% and can be a standard process for the growth integration of multicolor micro-LEDs.