Remarkable efficiency improvement in AlGaN-based ultraviolet light-emitting diodes using graded last quantum barrier

The optical properties of AlGaN-based deep ultraviolet light-emitting diodes (DUV LED) with step-graded AlInGaN last quantum barrier (LQB) are numerically studied. In contrast to conventional LQB, step-quaternary-graded last quantum barrier (QGLQB) exhibits enhancement in the internal quantum efficiency (IQE). This is attributed to the reduction in lattice mismatch, leading to suppressed leakage of electrons and enhanced hole transportation into the multiquantum well (MQW). Electrons are enhanced by ~124% whereas holes are enhanced by ~22% in the QGLQB structure. Moreover, the efficiency droop is also reduced from ~77% (conventional structure) to ~8% (proposed structure).