Nitride Quantum Structures in Optoelectronics – A Story of Colors

This review summarizes progress in the performance of nitride emitters across the full spectral range, with particular emphasis on the evolution of external quantum efficiency (EQE). Nitride emitters are primarily based on InGaN quantum wells, while AlGaN quantum wells are used for ultraviolet operation. Device performance is governed by the intrinsic properties of these structures, which also determine key physical challenges across different wavelength regions. Blue InGaN LEDs achieve the highest efficiencies (~60-80% EQE), while green devices are limited to ~20-35% due to the “green gap,” with further reduction (~5-20%) toward longer wavelengths. In the ultraviolet, AlGaN-based emitters exhibit lower performance due to material and structural challenges, although steady progress is being made. Special attention is given to mechanisms limiting EQE, including efficiency droop in the green-red region, and ongoing efforts to mitigate these effects. Finally, perspectives for future applications of nitride-based quantum structures in optoelectronics are outlined.