Resolving the electron-hole injection trade-off in AlGaN deep ultraviolet LEDs via polarization-coupled periodic heterostructures.

Deep ultraviolet (DUV) AlGaN-based light-emitting diodes (LEDs) are promising for sterilization and sensing applications, but are limited by low external quantum efficiency (EQE). Here, we demonstrate an electron-blocking-layer-free (EBL-free) architecture based on polarization-coupled periodic heterostructures (PPH) to overcome the trade-off between electron confinement and hole injection. Devices were grown by metal-organic chemical vapor deposition and analyzed using combined electroluminescence measurements and self-consistent simulations. The optimized structure, employing a five-period Al0.8Ga0.2N/Al0.6Ga0.4N p-type heterostructure, achieves a peak EQE of 7.8% and an output power of 67 mW at 261 nm, with negligible efficiency droop from 50 to 200 mA. Band and carrier analyses reveal that multi-step conduction barriers suppress electron leakage, while step-like valence bands and polarization-induced hole gas enhance hole injection and radiative recombination. This work provides a viable strategy for high-efficiency DUV LEDs and establishes a general framework for carrier engineering in wide-bandgap semiconductors.