Optical polarization characteristics for AlGaN-based light-emitting diodes with AlGaN multilayer structure as well layer

The optical properties of AlGaN-based quantum well (QW) structure with two coupled thin well layers are investigated by the six-by-six K–P method. Compared with the conventional structure, the new structure, especially the one with lower Al-content in the barrier layer, can enhance the TE-/TM-polarized total spontaneous emission rate due to the strong quantum confinement and wide recombination region. For the conventional QW structure, the reduction of well thickness can lead the degree of polarization (DOP) to decrease and the internal quantum efficiency (IQE) to increase. By using the coupled thin well layers, the DOP for the structure with high Al-content in the barrier layer can be improved, while the DOP will further decrease with low Al-content in the barrier layer. It can be attributed to the band adjustment induced by the combination of barrier height and well layer coupling. The IQE can also be further enhanced to 14.8%–20.5% for various Al-content of barrier layer at J = 100 A/cm². In addition, the efficiency droop effect can be expected to be suppressed compared with the conventional structure. (paper)