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Ultraviolet Light Emitting Diodes Grown on Sapphire and Silicon Carbide Substrates.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Ultraviolet Light Emitting Diodes Grown on Sapphire and Silicon Carbide Substrates./
Author:	Zollner, Christian J.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2022,
Description:	232 p.
Notes:	Source: Dissertations Abstracts International, Volume: 83-11, Section: B.
Contained By:	Dissertations Abstracts International83-11B.
Subject:	Electrical engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28968415
ISBN:	9798426839359

Ultraviolet Light Emitting Diodes Grown on Sapphire and Silicon Carbide Substrates.
Zollner, Christian J.

Ultraviolet Light Emitting Diodes Grown on Sapphire and Silicon Carbide Substrates. - Ann Arbor : ProQuest Dissertations & Theses, 2022 - 232 p.

Source: Dissertations Abstracts International, Volume: 83-11, Section: B.

Thesis (Ph.D.)--University of California, Santa Barbara, 2022.

This item is not available from ProQuest Dissertations & Theses.

Germicidal ultraviolet (GUV) light with wavelengths between 250 nm and 300 nm was first discovered to have a strong disinfectant effect in the 19th century. GUV irradiation is a chemical-free, species-agnostic disinfection technology: some example applications include disinfection of medical equipment and buildings; municipal water treatment, residential water purification, and consumer devices like water bottles; air disinfection in offices, schools, planes, cruise ships, and retail spaces, and countless others. Most importantly, a low-cost, durable, portable, and efficient solid-state GUV light source could bring these disinfection applications to low-income and developing regions where most sewage enters waterways untreated, and the lack of sterile environments and equipment worsens healthcare outcomes. The current incumbent technology for GUV light emission is the mercury lamp. This technology has remained largely unchanged for the past century—it is efficient and inexpensive, and has a large market due to its use for phosphor-converted white light (“fluorescent lighting”). On the other hand, this technology relies on toxic mercury vapor contained within a hot quartz bulb, requires complex and inefficient driving electronics, and cannot be reliably dimmed or rapidly switched on/off. To meet growing demand for disinfection technologies, and for GUV to expand into residential, consumer, and smart applications, a solid-state GUV light emitter is needed. A UV LED would have many benefits, much like the now-mature solid-state blue and white LEDs which have revolutionized the lighting and display industries. Semiconductor LEDs can be produced at smaller sizes, lower costs, higher efficiencies, and longer lifetimes than their 19th-century vapor lamp counterparts; these semiconductor devices can be dimmed or switched rapidly with no warm-up or flicker, and are readily produced in a variety of target wavelengths. Currently available UV LED technologies based on the AlGaN materials system are much less efficient (3–5%) than Hg lamps (20–30%), due to a number of challenges related to AlGaN material quality, chemical purity, process technologies, and optical properties. Therefore, there is a strong desire to improve the efficiency, cost, and lifetime of UV emitters to match their visible LED counterparts, which have efficiencies well over 50% and lifetimes over 10,000 h. In this dissertation, I discuss the ways in which AlN and AlGaN defect density on foreign substrates has been greatly reduced using improved MOCVD growth methods, achieving a dislocation density of 2 x 108 cm–2 on SiC. Next, I will explain why n-type and p-type doping (both of which are needed for LED operation) of AlGaN are challenging, and how both have been greatly improved using growth condition modification and polarization engineering, respectively. Using the methods outlined in this dissertation, we achieved n-type AlxGa1-xN (x > 0.65) resistivities below 10 mΩ-cm in material grown on three different substrate platforms (4H-SiC, 6H-SiC, and sapphire), and on two different MOCVD reactors. I will discuss active region engineering for increased light emission power, as well as an analysis of the various LED processing methods and packaging architectures used in the devices shown. Combining improvements in material quality, electrical conductivity, and optical quality, we have increased GUV LED external quantum efficiency from 2% to 10%.

ISBN: 9798426839359Subjects--Topical Terms:

596380
Electrical engineering.
Subjects--Index Terms:

AlGaN

Ultraviolet Light Emitting Diodes Grown on Sapphire and Silicon Carbide Substrates.
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245 1 0 $a Ultraviolet Light Emitting Diodes Grown on Sapphire and Silicon Carbide Substrates.
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300 $a 232 p.
500 $a Source: Dissertations Abstracts International, Volume: 83-11, Section: B.
500 $a Advisor: Nakamura, Shuji.
502 $a Thesis (Ph.D.)--University of California, Santa Barbara, 2022.
506 $a This item is not available from ProQuest Dissertations & Theses.
506 $a This item must not be sold to any third party vendors.
520 $a Germicidal ultraviolet (GUV) light with wavelengths between 250 nm and 300 nm was first discovered to have a strong disinfectant effect in the 19th century. GUV irradiation is a chemical-free, species-agnostic disinfection technology: some example applications include disinfection of medical equipment and buildings; municipal water treatment, residential water purification, and consumer devices like water bottles; air disinfection in offices, schools, planes, cruise ships, and retail spaces, and countless others. Most importantly, a low-cost, durable, portable, and efficient solid-state GUV light source could bring these disinfection applications to low-income and developing regions where most sewage enters waterways untreated, and the lack of sterile environments and equipment worsens healthcare outcomes. The current incumbent technology for GUV light emission is the mercury lamp. This technology has remained largely unchanged for the past century—it is efficient and inexpensive, and has a large market due to its use for phosphor-converted white light (“fluorescent lighting”). On the other hand, this technology relies on toxic mercury vapor contained within a hot quartz bulb, requires complex and inefficient driving electronics, and cannot be reliably dimmed or rapidly switched on/off. To meet growing demand for disinfection technologies, and for GUV to expand into residential, consumer, and smart applications, a solid-state GUV light emitter is needed. A UV LED would have many benefits, much like the now-mature solid-state blue and white LEDs which have revolutionized the lighting and display industries. Semiconductor LEDs can be produced at smaller sizes, lower costs, higher efficiencies, and longer lifetimes than their 19th-century vapor lamp counterparts; these semiconductor devices can be dimmed or switched rapidly with no warm-up or flicker, and are readily produced in a variety of target wavelengths. Currently available UV LED technologies based on the AlGaN materials system are much less efficient (3–5%) than Hg lamps (20–30%), due to a number of challenges related to AlGaN material quality, chemical purity, process technologies, and optical properties. Therefore, there is a strong desire to improve the efficiency, cost, and lifetime of UV emitters to match their visible LED counterparts, which have efficiencies well over 50% and lifetimes over 10,000 h. In this dissertation, I discuss the ways in which AlN and AlGaN defect density on foreign substrates has been greatly reduced using improved MOCVD growth methods, achieving a dislocation density of 2 x 108 cm–2 on SiC. Next, I will explain why n-type and p-type doping (both of which are needed for LED operation) of AlGaN are challenging, and how both have been greatly improved using growth condition modification and polarization engineering, respectively. Using the methods outlined in this dissertation, we achieved n-type AlxGa1-xN (x > 0.65) resistivities below 10 mΩ-cm in material grown on three different substrate platforms (4H-SiC, 6H-SiC, and sapphire), and on two different MOCVD reactors. I will discuss active region engineering for increased light emission power, as well as an analysis of the various LED processing methods and packaging architectures used in the devices shown. Combining improvements in material quality, electrical conductivity, and optical quality, we have increased GUV LED external quantum efficiency from 2% to 10%.
590 $a School code: 0035.
650 4 $a Electrical engineering. $3 596380
650 4 $a Physics. $3 564049
650 4 $a Materials science. $3 557839
653 $a AlGaN
653 $a Epitaxy
653 $a MOCVD
653 $a Semiconductor
653 $a Ultraviolet
653 $a Ultrawide bandgap
690 $a 0794
690 $a 0544
690 $a 0605
710 2 $a University of California, Santa Barbara. $b Materials. $3 1187227
773 0 $t Dissertations Abstracts International $g 83-11B.
790 $a 0035
791 $a Ph.D.
792 $a 2022
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28968415