All-InGaN/GaN red light-emitting diodes with low-temperature-grown GaN capping layer

The growth of indium-rich InGaN red light-emitting diodes (LEDs) is essential for realizing all-nitride full-color micro-LED displays. This study presents a strategy for fabricating red LEDs with InGaN/GaN multiple quantum wells (MQWs) by introducing a low-temperature-grown GaN quantum-well capping (LT-GaN QC) layer, without the need for strain-engineered structures. The insertion of LT-GaN QC induces a significant electroluminescence (EL) wavelength shift of MQWs from 506 to 668 nm. This capping layer effectively suppresses indium re-evaporation and sequential InGaN decomposition during the subsequent high-temperature growth of quantum barriers (QBs). Quantitative structural analyses using transmission electron microscopy and energy-dispersive x-ray spectroscopy confirm that the thickness of the LT-GaN QC strongly influences both the QW thickness and indium composition. These findings demonstrate that the LT-GaN QC layer provides a practical approach to preserving indium-rich InGaN QWs during high-temperature processes, thereby enabling the fabrication of high-efficiency nitride-based red and longer-wavelength LEDs.