Rational Superlattice Electron Blocking Layer Design for Boosting the Quantum Efficiency of 371 nm Ultraviolet Light-Emitting Diodes

Although great progress has been made in InGaN/AlGaN ultraviolet light-emitting diodes (UV LEDs), their quantum efficiency is still suffering from severe electron leakage and poor hole injection. Here, we propose AlInGaN/AlGaN superlattice electron blocking layer (SEBL) to enhance the electron confinement and hole injection of UV LEDs emitting at 371 nm. Experimental result shows that the UV LED with AlInGaN/AlGaN SEBL achieves a 21% enhancement in light output power (LOP) at 60 mA and a slight reduction in forward voltage and compressive stress, compared to the UV LED with conventional AlInGaN EBL. Numerical simulation reveals the underlying mechanism that the AlInGaN/AlGaN SEBL enables energy band modulation. The less tilted energy band of quantum wells due to strain relaxation could mitigate the separation of carrier wave functions. The increased effective barrier height for electrons and notches in the conduction band of SEBL could block the electrons overflowing into the p-region. Furthermore, holes are found to accumulate in spikes of the valance band of SEBL, thereby effectively facilitating hole injection and enhancing the radiative recombination rate.