Electron Confinement and Hole Injection Improvement in InGaN/GaN Light-Emitting Diodes With Graded-Composition Last Quantum Barrier and Without Electron Blocking Layer

The highly magnesium (Mg)-doped wide-bandgap AlGaN electron blocking layer (EBL) is widely used in InGaN/GaN light-emitting diodes (LEDs) for electron leakage suppression. However, the EBL also reduces the hole injection efficiency and high Mg doping in AlGaN is a challenging. In this work, InGaN/GaN LEDs with a graded-composition AlGaN last quantum barrier and without the conventional AlGaN electron blocking layer were proposed and investigated numerically. Using the proposed structure, the optical output power and the efficiency droop are improved significantly when compared with the corresponding properties of conventional LEDs. The simulation results indicate that these improvements can be attributed to increments in both the electron confinement and the hole injection efficiency because of the appropriate energy band structure design of the LEDs.