The efficiency of ultra violet LEDs is critically limited by the absorption losses in p-type and metal layers. In this work, surface roughening based light extraction structures are combined with tunneling-based top-contacts to realize highly efficient top-side light extraction efficiency in UV LEDs. Surface roughening of the top n-type AlGaN contact layer is demonstrated using self-assembled Ni nano-clusters as etch mask. The top surface roughened LEDs were found to enhance external quantum efficiency by over 40% for UV LEDs with a peak emission wavelength of 326 nm. The method described here can enable highly efficient UV LEDs without the need for complex manufacturing methods such as flip chip bonding.
@article{arxiv.1512.02260,
title = {Enhanced Light Extraction in Tunnel Junction Enabled Top Emitting UV LEDs},
author = {Yuewei Zhang and Andrew Allerman and Sriram Krishnamoorthy and Fatih Akyol and Michael W. Moseley and Andrew Armstrong and Siddharth Rajan},
journal= {arXiv preprint arXiv:1512.02260},
year = {2016}
}