AlGaN-Based DUV LEDs With Al-Composition-Engineered AlGaN Superlattice Inserted at the p-EBL/Hole Supplier Interface

For 0001-oriented AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs), the severe electron leakage and poor hole injection efficiency significantly decline the external quantum efficiency (EQE) and optical power. In this work, we propose an insertion structure of Al $_{\text{x}}$ Ga $_{\text{1}-\text{x}}$ N/Al $_{\text{y}}$ Ga $_{\text{1}-\text{y}}$ N superlattice (SL) positioned between the p-type electron blocking layer (p-EBL) and the hole supplier layer (HSL), featuring a gradually decreasing Al composition within each well and barrier. Reduced potential barrier height for holes at the p-EBL/HSL interface can be achieved by the integration of the proposed SL structure, thereby augmenting the hole concentration in the active region. Besides, the net negative polarization charges generated across the embedded SL structure can facilitate the acceptor ionization and enhance hole injection efficiency. On the other hand, the inserted SL layer can effectively elevate the potential barrier height of electrons at the p-type region, consequently suppressing electron leakage. Therefore, compared to the reference DUV LEDs, the proposed DUV LEDs with the Al-composition-engineered SL insertion structure exhibit a 39.3% improvement in the EQE along with an 83.7% reduction in efficiency droop at 100 A/cm $^{\text{2}}$ . This design strategy offers an effective approach to improving the optoelectronic performance of DUV LEDs.