Abstract
We presented a compositionally graded hole reservoir layers(HRL) - an AlGaN/GaN super lattice hole reservoir layer with Al mole fraction multi-step gradient from high to low (GSL-HRL) in this paper. The designed LED with compositionally step graded HRL shows comparable low operating voltage and less efficiency droop. Simulation results reveal that this graded HRL could reserve the hole effectively and the hole in HRL can be energized by the strong electric field due to the polarization caused by different Al contents AlxGa1-xN layers. Such a design makes hole travel across the p-type EBL and inject into the MQWs more efficiently and smoothly. The novel structure of HRL improves the performance of the LED significantly and gives a promising application in high power GaN-based LED in the future.
Highlights
To dominate the solid-state lighting market, applications of high-power III-nitride InGaN/GaN light-emitting diodes (LEDs) at high injection current density must be prevailing.[1,2,3] for high-power GaN-based LEDs, one of the most significant and enduring challenges is the efficiency droop: the decrease of external quantum efficiency (EQE) with increasing drive current in the LED
A poor hole-injection efficiency is known as a common problem in GaNbased LEDs because of low Mg activation efficiency and the asymmetric transport ability of electrons and holes.[8]
Zhang et al used a hole accelerator to accelerate the holes and achieved the enhanced external quantum efficiency (EQE) of ∼15%, and the efficiency droop was reduced from ∼54.2% to ∼35.9% at 100 A/cm[2], experimentally
Summary
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