Increasing the Luminescence Efficiency of Long-Wavelength (In,Ga)N Quantum Well Structures by Electric Field Engineering Using an (Al,Ga)N Capping Layer

Despite the very high efficiency at blue wavelengths, nitride-based light-emitting diodes suffer from low efficiencies in the green and red spectral ranges. Different solutions have been proposed to mitigate the "green gap,"including the addition of an (Al,Ga)N capping layer to the quantum well structure. In this work, we show how the increased polarization field due to such an (Al,Ga)N capping layer has profound effects on carrier location and recombination probabilities. The proper choice of (Al,Ga)N composition leads to an increased electron-hole overlap as well as an enhanced confinement in the quantum well region. Therefore, the combination of band structure and electric field engineering can be a promising approach to mitigate the green gap problem.