Droop-multimode trade-off in GaN-InGaN LEDs: Effect of polarization-matched AlInGaN blocking layers

Polarization-matched graded AlInGaN electron blocking layer (EBL) and hole blocking layer (HBL) are proposed to reduce efficiency droop in GaN-InGaN light-emitting diodes (LEDs). Five different structures have been simulated to study the effect of different blocking layers and a significant reduction in the efficiency droop has been noticed, from 52% in conventional structure to 2% in polarization-matched graded AlInGaN EBL and HBL structure at a current density of 1000 A cm−2. This has been achieved at the cost of multimode emission from such polarization-matched blocking layers which sets a trade-off between efficiency droop and multimode emission. The AlInGaN layer can therefore be characterized by droop cut-off condition (DCC) and multimode cut-off condition (MCC). For the best structure proposed in this paper, simulations indicate a DCC having Al and In composition of 0.10 and 0.15 respectively; and an MCC having Al and In composition of 0.08 and 0.23 respectively.