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In this study, a new design on last quantum barrier (LQB) is investigated numerically with the purpose of improving the optical performance of InGaN light-emitting diodes (LEDs). Through the analysis of the energy band diagrams, electrostatic fields, carrier concentrations, carrier current densities, and radiative recombination rates, we have got the simulation results that the proposed undoped-InGaN/AlInGaN superlattice (SL) LQB can significantly improve the output power and internal quantum efficiency, which is mainly attributed to the successful improvement in hole injection efficiency and suppression of electron current leakage. Moreover, the efficiency droop of the LEDs is improved slightly by using u-InGaN/AlInGaN SL as last barrier.

With the purpose to increase the uniformity of carrier distribution without sacrificing the enhancement of carrier injection efficiency, the light-emitting diodes (LEDs) without an electron-blocking layer (EBL) by using AlGaN step-like barriers (SLBs) is proposed and investigated numerically. The simulation results show that the enhanced electron confinement and hole injection efficiency are mainly attributed to the mitigated downward band bending induced by polarization field at the interface of the last barrier and EBL and the increased carrier distribution uniformity is due to step-like potential height for carrier of the new designed LEDs. In addition, the distribution of radiative recombination rate and the efficiency droop are markedly improved when the conventional GaN barriers are replaced by AlGaN SLBs and the EBL is removed.

The blue InGaN light-emitting diodes (LEDs), employing a lattice-compensated p-AlGaN/InGaN superlattice (SL) interlayer to link the last quantum barrier and electron blocking layer (EBL), are proposed and investigated numerically. The simulation results indicate that the newly designed LEDs have better hole injection efficiency, lower electron leakage, and smaller electrostatic fields in the active region over the conventional LEDs mainly attributed to the mitigated polarization-induced downward band bending. Furthermore, the markedly improved output power and efficiency droop are also suggested when the conventional LEDs corresponding to experiment data are replaced by the newly designed LEDs.