Color-tuning of InGaN quantum discs by molecular beam epitaxy

InGaN quantum discs (QDCs), grown in nanowires by molecular beam epitaxy on patterned substrates, have recently received significant attention for their application in micro-light-emitting diodes and lasers. Despite the existing efforts and progress, it remains unclear which is the key design parameter for tuning the light emission wavelength of such QDCs, impeding their development. In this study, we pinpoint the key design parameter by comparing the light emission properties of InGaN QDCs embedded in GaN nanowire hosts with various designs. We find that the light emission wavelength can be effectively tuned by the gap size between nanowires, rather than the nanowire diameter or the period of the pattern. The same gap means a negligible shift in the light emission wavelength, whereas a reduced gap means a redshift. A detailed phenomenological explanation considering the effects induced by reducing the nanowire gap size is provided. This study provides a practical guide to the design of the light emission wavelength of InGaN QDCs.