InGaN Ultraviolet Light-Emitting Diodes Grown on Patterned Sapphire Substrates

• Main Authors: Chi-Hsun Hsieh, 謝奇勳
• Other Authors: 綦振瀛
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/36679725321973560354

碩士 === 國立中央大學 === 電機工程研究所 === 95 === Near ultraviolet GaN/InGaN multi-quantum-well light-emitting diodes (LEDs) have been grown on stripe-patterned sapphire substrates (PSSs) and investigated. The correlation between the stripe orientation, etching depth, dislocation density, and the electrical and optical properties of the 400 nm LEDs are examined and compared with the LEDs grown on planar sapphire substrates. Etching conditions have been systemically studied by varying the composition of etching solutions and etching temperatures. Symmetric and asymmetric etching profiles are observed as the stripe patterns are defined along the <1-100>sapphire and <11-20>sapphire direction, respectively. Based on the etch pits density experiments, dislocation density of GaN can be reduced by over 3 times as the patterned sapphire substrates are used. The output power of <11-20> PSS-LEDs is enhanced by 21%, 44% and 87% as the etching depth is 0.2, 0.5 and 0.9 μm, respectively. On the other hand, the output power of <1-100> PSS-LEDs is enhanced by 37%, 72% and 163% as the etching depth is 0.2, 0.5 and 0.9 μm, respectively. The radiation angle of LEDs is also found to decrease from 148o to 120o with increasing groove depth from 0 to 0.9 μm while similar radiation angle is observed for the LEDs grown on PSS with stripes along different directions.