Advantages of AlGaN-Based 310-nm UV Light-Emitting Diodes With Al Content Graded AlGaN Electron Blocking Layers

In order to improve the performance of deep ultraviolet light-emitting diodes (UV LEDs), the effects of different electron blocking layers (EBLs) on the performance of Al_xGa_1-xN-based deep UV LEDs at 310 nm have been studied through a numerical simulation. The simulation results show that the adoption of EBLs is critical to improve the device performance. In comparison with a conventional structure using EBL with constant Al composition (0.7), the device structure with an Al-content graded Al_xGa_1-xN (from 0.9 to 0.4 in the growth direction) EBL possesses numerous advantages such as lower working voltage, higher internal quantum efficiency, and less efficiency droop under high-current injection. By detailedly analyzing the profiles of energy band diagrams, distributions of carrier concentration, and electron current density, the advantages of Al-content graded Al_xGa_1-xN EBL are attributed to the resulting lower resistivity, higher barrier for electron leakage, and simultaneously reduced barrier for hole injection compared with the conventional EBL with constant Al composition.