Design of Hole-Blocking and Electron-Blocking Layers in Al_xGa_1-xN-Based UV Light-Emitting Diodes

The band-engineered structure design for electron-blocking layer (EBL) and hole-blocking layer (HBL) in Al_xGa_1-xN-based ultraviolet light-emitting diodes (UV LEDs) is performed and analyzed theoretically. Simulation results show that the severe polarization effect is efficiently mitigated and the downward-bended band profile of the EBL is improved when the EBL is designed with a graded-composition and multiquantum barrier (GMQB) structure. As a result, the capabilities of both electron confinement and hole injection, and also the light output power are promoted. On the contrary, for the HBL, the design of composition graded and/or multiquantum barrier structures reduces the effective potential barrier height for holes in the valence band and, consequently, causes a considerable hole overflow. The UV LED, thus, exhibits superior optical performance when the LED structure is simultaneously designed with a GMQB EBL and a bulk HBL.