Enhancing extraction efficiencies of light-emitting diodes with distributed bragg reflectors
Date Issued
2009
Date
2009
Author(s)
He, Tzung-Yu
Abstract
Recently, wide-band-gap semiconductors have been attracting great interest for applications to optoelectronic devices such as light-emitting diodes (LEDs). For last few years, InGaN/GaN-based blue light-emitting diodes (LEDs) have been successfully fabricated and following comes the epochal of white light LED.However, for future illumination applications, it is a very important topic to further enhance the external quantum efficiency of LEDs. In this thesis, we deposited the distributed bragg reflector on the backside of LED chips to improve the extraction efficiency and light characteristic of a white light LED module. First, the optical software TFCalc was used to design the distributed bragg reflector. And the optical software TracePro was used to design the LED module. We finally compared the simulation result with the actual experiment result. We used the optical software TFCalc to design different DBR structures. Then we set the reflectivity of the optimized DBR structure to the surface property of TracePro. We established the simulation model by TracePro software for the white light LED using a blue LED chip with YAG:Ce phosphor. We could simulate how the extraction efficiency of LED model was enhanced by the DBR. The designed DBR was deposited on the backside of LED chips which were packaged and measured. Depositing DBR on the backside of LED chips was more helpful for enhancing the extraction efficiency of bigger LED chip size. The light output power enhancement of 13 mil-13 mil LED chip was 9.65%, but that was 31.85% for the 45mil-45 mil LED chip. Depositing DBR on the backside of LED chips was one of the ways to enhance the extraction efficiency of LED model.
Subjects
LED
DBR
light extraction efficiency
Type
thesis
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