Efficiency Improvements in AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes with Graded Superlattice Last Quantum Barrier and Without Electron Blocking Layer

The characteristics of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) with electroluminescence peak wavelength of emission about 289 nm have been investigated by optimizing the last quantum barrier (LQB) in the active region. The results demonstrate that the internal quantum efficiency and radiative recombination rate of DUV-LEDs with a graded superlattice last quantum barrier (GSL LQB) and without an electron blocking layer (EBL) are higher than for other structures under current of 180 mA. Also, the electron and hole leakage currents are reduced for the GSL LQB structure. This structure contributes to effective electron confinement and hole injection owing to increased overlap of electron and hole wavefunctions resulting from low electrostatic fields in the active region. As a result, the optical output power of the structure with a GSL LQB and without an EBL is increased by 1.62 times, and the spontaneous emission intensity by 1.56 times, compared with the conventional structure.