Improved efficiency droop characteristics in InGaN/GaN light-emitting diode with a novel designed last barrier structure

In this study, the characteristics of the nitride-based light-emitting diodes with different last barrier structures are analysed numerically. The energy band diagrams, electrostatic field near the last quantum barrier, carrier concentration in the quantum well, internal quantum efficiency, and light output power are systematically investigated. The simulation results show that the efficiency droop is markedly improved and the output power is greatly enhanced when the conventional GaN last barrier is replaced by AlGaN barrier with Al composition graded linearly from 0 to 15% in the growth direction. These improvements are attributed to enhanced efficiencies of electron confinement and hole injection caused by the less polarization effect at the last-barrier/electron blocking layer interface when the graded Al composition last barrier is used.