High external quantum efficiency (6.8%) UV-A LEDs on AlN templates with quantum barrier optimization
Yifan Yao, Hongjian Li, Michael Wang, Panpan Li, Michael Lam, Michael Iza, James S. Speck, Steven P. DenBaars, Shuji Nakamura
Abstract
AlGaN-based UV-A LEDs have wide applications in medical treatment and chemical sensing; however, their efficiencies are still far behind visible LEDs or even shorter wavelengths UV-C counterparts because of the large lattice mismatch between the low-Al-content active region and the AlN substrate. In this report, we investigated the composition and thickness of the quantum barrier in the active region in terms of LED performance. Due to the improved strain management and better carrier confinement, efficient UV-A LEDs (320 nm - 330 nm) with EQEs up to 6.8% were demonstrated, among the highest efficiencies at this wavelength range.