Enhancing the Hole Injection in AlGaN-Based Deep Ultraviolet Light-Emitting Diodes With Engineered p-AlGaN Hole Supplier Layer

The poor hole injection severely constrains the external quantum efficiency (EQE) and light output power (LOP) of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs). This constraint primarily stems from the insufficient energy of holes, which is strongly influenced by the p-AlGaN electric field within the hole supplier layer (HSL) for AlGaN-based DUV LEDs. In this work, we propose the incorporation of multiple thin p-AlGaN insertion layers into an Al-composition-decreasing (ACD) p-AlGaN HSL to enhance the hole injection efficiency. Significant enhancements in both EQE and LOP are observed for the investigated DUV LEDs under different current injection densities. Through analyzing the fundamental physical mechanism underlying the improved hole injection achieved by this proposed structure, we attribute these enhancements to the augmentation of the hole-accelerating electric field, facilitated by polarization-induced sheet charges at the related interfaces of the insertion layers, and the strong intraband tunneling processes for holes, favored by ultrathin insertion layers. Meanwhile, the accumulation of holes at the upper interface of the insertion layers and the existence of three-dimensional hole gas (3DHG) in the ACD p-AlGaN HSL further contribute to the enhanced hole injection. The proposed ACD p-AlGaN HSL design with the incorporation of multiple thin p-AlGaN insertion layers provides a promising approach for elevating the performance of DUV LEDs.