Rapid efficiency roll-off in high-quality green light-emitting diodes on freestanding GaN substrates

Yang, Y.; Cao, X. A.; Yan, C. H.
January 2009
Applied Physics Letters;1/26/2009, Vol. 94 Issue 4, pN.PAG
Academic Journal
InGaN/GaN multiple-quantum-well green light-emitting diodes (LEDs) were grown on freestanding GaN and sapphire substrates. The density of microstructural defects in the LED on GaN was substantially reduced, leading to a significant reduction in defect-assisted tunneling currents and an improved injection efficiency under low bias. The LED on GaN outperformed the LED on sapphire at low injection currents and exhibited a ∼65% peak internal quantum efficiency. However, it suffered from even more dramatic efficiency roll-off, which occurs at a current density as low as 0.3 A/cm2. This behavior is explained as the combined result of efficient current injection and significant carrier overflow in a high-quality LED.


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