Title page for etd-0715104-015852


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URN etd-0715104-015852
Author Jing-Ru Chen
Author's Email Address m9131601@student.nsysu.edu.tw
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Department Electrical Engineering
Year 2003
Semester 2
Degree Master
Type of Document
Language English
Title Enhancement of Light Extraction of GaN Blue Light Emitting Diode
Date of Defense 2004-07-09
Page Count 83
Keyword
  • GaN LED
  • Reflector
  • Phororesist Microlenses
  • Flip-Chip technique
  • Abstract In recent years, even though the light output of GaN-based LED continues to increase, the brightness (~20 lm/W) is still low compared to conventional lighting systems and it is necessary to further improve the light extraction of LEDs.
    In this study, we utilize flip-chip technique, photoresist microlenses, reflectors and thermoelectric cooler to increase the light extraction of GaN MQW LED. Electroluminescence (EL) and power angular distribution are used to measure the light output intensity of LED. From temperature dependent current-voltage (I-V-T) characteristics, the charge carrier transport mechanisms at different biased regions are also investigated.
    In the results, back emission of LED with SiO2/Al reflector has maximum light intensity ( 3.28μW ) , which is higher than front emission one ( 2.73μW ) in vertical emitting area ( at 90 angles). LED with P.R. microlenses (refractive index, n=1.62) on backside could improve the light extraction of LED (about 1.2 times) as well. The enhancement of light output is duo to the reduction of light absorption from the metal contact and Fresnel’s transmission losses at GaN (n=2.4)/air (n=1) interface.
    Finally, we fabricate a high brightness LED with above light enhancement design. EL intensity of LED is increased about 1.25 times than conventional one. Therefore, we can manufacture a LEDs array with above designs to obtain high light output for future solid-state illumination.
    Advisory Committee
  • Jeng Gong - chair
  • Tsu-Hsin Chang - co-chair
  • Wen-Tai Lin - co-chair
  • Ming-Kwei Lee - advisor
  • Files
  • etd-0715104-015852.pdf
  • indicate in-campus access in a year and off_campus not accessible
    Date of Submission 2004-07-15

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