Mechanism of suppressing efficiency droop by modulating the thickness of quantum barriers in light-emitting diodes

In this paper, modulating the thickness of quantum barriers (QBs) in gallium nitride (GaN) based light-emitting diodes (LEDs) has been investigated numerically and experimentally. To reveal the underlying mechanism of efficiency droop for LEDs with different QB thicknesses, the dualwavelength active regions were specially designed. Compare to LEDs with 18-nm-thick QBs and 9-nm-thick QBs, the efficiency droop ratio of the LED with 12-nm-thick QBs is the lowest at the high current density of 80A/cm2, which indicates that LEDs with medium QB thickness are the best for suppressing efficiency droop. The measured external quantum efficiency (EQE) of the LED with 18-nm-thick QBs is the highest at the low current density of 5A/cm2, which may result from the lowest leakage current. However, due to the higher hole injection level, the measured EQE results of the LED with 12-nm-thick QBs are higher than the LED with 18-nm-thick QBs at 80A/cm2.