Efficiency enhancement of blue InGaN LEDs with indium composition graded InGaN barriers

In recent literatures, the quantum efficiency of conventional blue InGaN light-emitting diodes (LEDs) is quite limited under relatively high driving current with conventional GaN barriers due presumably to the poor injection efficiency of hole. In this study, the efficiency enhancement of blue InGaN LEDs with indium composition graded InGaN barriers is proposed. The energy band diagram, carrier concentration in the quantum wells, diagram of hole current, radiative recombination rate, L-I curves, and internal quantum efficiency are investigated numerically. The simulation results show that the InGaN LED with graded InGaN barriers has better performance over its conventional counterpart with GaN barriers due to enhanced efficiency of hole injection. The simulation results also suggest that under relatively high current injection, the internal quantum efficiency and output light power are markedly improved when the traditional GaN barriers are replaced by graded InGaN barriers. According to the improved optical properties, the new-designed LED has promising potential in solid state lighting.