Effect of N-Type AlGaN Layer on Carrier Transportation and Efficiency Droop of Blue InGaN Light-Emitting Diodes

The effect of an n-type AlGaN layer on the physical properties of blue InGaN light-emitting diodes (LEDs) is investigated numerically. The p-type AlGaN electron-blocking layer is usually used in blue LEDs to reduce the electron leakage current. However, the p-type AlGaN layer also retards the injection of holes, which leads to the degradation of efficiency at high current. To improve the efficiency droop of blue InGaN LEDs at high current, an n-type AlGaN layer below the active region is proposed to replace the traditional p-type AlGaN layer. The simulation results show that the improvement in efficiency droop is due mainly to the sufficiently reduced electron leakage current and more uniform distribution of holes in the quantum wells.