Light Extraction Efficiency Analysis of Flip-Chip Ultraviolet Light-Emitting Diodes With Patterned Sapphire Substrate

Light Extraction Efficiency Analysis of Flip-Chip Ultraviolet Light-Emitting Diodes With Patterned Sapphire Substrate

This study investigates polarization-dependent light extraction efficiency (<italic>&#x03B7;</italic><sub>extraction </sub>) of AlGaN-based flip-chip ultraviolet (UV) light-emitting diodes (LEDs) emitting at 230 nm and 280&#x00A0;nm with microdome-shaped patterning on...

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Bibliographic Details
Main Authors: Yu Kee Ooi, Jing Zhang
Format: Article
Language:English
Published: IEEE 2018-01-01
Series:IEEE Photonics Journal
Subjects:
Patterned sapphire substrate
polarization-dependent light extraction efficiency
quantum well structure
ultraviolet light-emitting diodes.
Online Access:https://ieeexplore.ieee.org/document/8384025/
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Summary:This study investigates polarization-dependent light extraction efficiency (<italic>&#x03B7;</italic><sub>extraction </sub>) of AlGaN-based flip-chip ultraviolet (UV) light-emitting diodes (LEDs) emitting at 230 nm and 280&#x00A0;nm with microdome-shaped patterning on sapphire substrate based on 3-D finite-difference time-domain simulations. Three types of patterned sapphire substrates (PSS) have been analyzed: bottom-side PSS, top-side PSS, and double-sided PSS. Our results show that microdome-shaped patterning on sapphire substrate is predominantly beneficial in enhancing transverse-magnetic (TM)-polarized output. Specifically, TM-polarized <italic>&#x03B7;</italic><sub>extraction</sub> enhancement of up to &#x223C;4.5 times and &#x223C;2.2 times can be obtained for 230 nm and 280 nm UV LEDs with bottom-side PSS, respectively, and &#x223C;6.3 times and &#x223C;1.8 times for 230 nm and 280 nm UV LEDs with top-side PSS, respectively. By employing double-sided PSS, up to &#x223C;11.2 times and &#x223C;2.6 times enhancement in TM-polarized <italic>&#x03B7;</italic><sub>extraction</sub> can be achieved for 230 nm and 280 nm UV LEDs, respectively. In contrast, the microdome-shaped PSS act as a reflector for transverse-electric-polarized photons which leads to severe limitation in light extraction for both 230 nm and 280 nm flip-chip UV LEDs. Thus, it is expected that this study will serve as a guidance in designing PSS for high-efficiency mid- and deep-UV LEDs.
ISSN:1943-0655

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