Design of Wide-Bottomed Patterned Sapphire Substrates for Performance Improvement of GaN-Based Light-Emitting Diodes

We propose patterned sapphire substrates (PSSs) with wide-bottomed cone-shaped patterns to enhance the light extraction efficiency of GaN-based light-emitting diodes (LEDs). Simulation reveals that PSS with wide-bottomed cone-shaped patterns is of higher yield in LED light extraction efficiency. The subsequent fabrication of and epitaxial growth of LED structure on the proposed wide-bottomed PSS verify the simulation results experimentally. It is demonstrated that wide-bottomed patterns with narrow distance between patterns can effectively release stress, avoid the decline in crystal quality and improve light extraction efficiency. By comparison with the popular commercially available PSS, LED grown on the proposed PSS whose wide-bottomed patterns are of 3.91 mu m in width, 2.37 mu m in height and 0.09 mu m in distance is proven to be of as high as 16.7% improvement in luminous efficacy and 33.8% drop in dislocation density, which shows the promising future for its application in the highly efficient LEDs. (C) 2014 The Electrochemical Society. All rights reserved.