Enhancement of light extraction on AlGaN-based deep-ultraviolet light-emitting diodes using a sidewall reflection method

AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) suffer serious light extraction problems. In this work we report a sidewall reflection method to enhance the light extraction of AlGaN-based DUV LEDs. The method includes mesa micro array designs and on-chip high reflective metal pads for DUV light. The 278-nm LEDs using this method show a 30.% improvement in light output power (LOP) compared to LEDs without high reflective metal pads. The dependence of LOP and voltage on micro array mesa size is also investigated. The LOP of the AlGaN-based DUV LED can reach 6.8 mW at 100 mA and nearly 25 mW at 500 mA. The L80 lifetime exceeds 4000 hours.

[1]  Motoaki Iwaya,et al.  Realization of extreme light extraction efficiency for moth‐eye LEDs on SiC substrate using high‐reflection electrode , 2010 .

[2]  Takashi Jimbo,et al.  Optical properties of wurtzite structure GaN on sapphire around fundamental absorption edge (0.78–4.77 eV) by spectroscopic ellipsometry and the optical transmission method , 1997 .

[3]  Youngsoo Park,et al.  An elegant route to overcome fundamentally-limited light extraction in AlGaN deep-ultraviolet light-emitting diodes: Preferential outcoupling of strong in-plane emission , 2016, Scientific reports.

[4]  A. Selskis,et al.  A systematic study of light extraction efficiency enhancement depended on sapphire flipside surface patterning by femtosecond laser , 2015 .

[5]  Joon Seop Kwak,et al.  Light-extraction efficiency control in AlGaN-based deep-ultraviolet flip-chip light-emitting diodes: a comparison to InGaN-based visible flip-chip light-emitting diodes. , 2015, Optics express.

[6]  Patrick Vogt,et al.  Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes , 2010 .

[7]  Toru Kinoshita,et al.  Light extraction enhancement of 265 nm deep-ultraviolet light-emitting diodes with over 90 mW output power via an AlN hybrid nanostructure , 2015 .

[8]  S.C. Wang,et al.  Luminance Enhancement of Flip-Chip Light-Emitting Diodes by Geometric Sapphire Shaping Structure , 2008, IEEE Photonics Technology Letters.

[9]  Henri Benisty,et al.  Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution , 2006 .

[10]  M. Weyers,et al.  Advances in group III-nitride-based deep UV light-emitting diode technology , 2010 .

[11]  Michael S. Shur,et al.  AlGaN Deep-Ultraviolet Light-Emitting Diodes with External Quantum Efficiency above 10% , 2012 .

[12]  Michael W. Moseley,et al.  Influence of optical polarization on the improvement of light extraction efficiency from reflective scattering structures in AlGaN ultraviolet light-emitting diodes , 2014 .

[13]  Zhaoyang Fan,et al.  Nitride deep-ultraviolet light-emitting diodes with microlens array , 2005 .

[14]  Enhanced Light Output of GaN-Based Light-Emitting Diodes by Using Omnidirectional Sidewall Reflectors , 2007, IEEE Photonics Technology Letters.

[15]  James S. Speck,et al.  Chip Shaping for Light Extraction Enhancement of Bulk c-Plane Light-Emitting Diodes , 2012 .

[16]  J. Pastrňák,et al.  Refraction Index Measurements on AlN Single Crystals , 1966 .

[17]  Haizhong Xie,et al.  Light extraction efficiency improvement by multiple laser stealth dicing in InGaN-based blue light-emitting diodes. , 2012, Optics express.

[18]  S. Inoue,et al.  Enhanced wall-plug efficiency in AlGaN-based deep-ultraviolet light-emitting diodes with uniform current spreading p-electrode structures , 2016 .