Auger as Reason for Droop?

At this February’s Photonics West Conference, Joachim Piprek did a quick survey asking the audience which of the currently proposed mechanisms they thought to be responsible for the efficiency droop in GaN-based devices. The vast majority supported Auger as the dominant cause. I guess, this should not be surprising, seeing how this theory is pushed much more forcefully than any other.

In 2007, Philips Lumileds Lightning Co. declared it had “fundamentally solved” the droop problem, later revealing that they identified Auger losses as the culprit. In 2009, when intraband Auger processes were suggested as dominant process by K.T. Delaney, et al. (Appl. Phys. Lett. 94, 191109 (2009)), the authors concluded: “The calculated values … confirm that Auger recombination is a key loss mechanism in nitride light emitters.”  Two years later, calculations by E. Kioupakis, et al. shifted the blame to indirect Auger processes (Appl. Phys. Lett. 98, 161107 (2011)). One of the authors, C. Van de Walle, declared: “With Auger recombination now established as the culprit [for the droop] …”.