Charge Carrier Diffusion Induced Light Emitting Diodes
(2024)- Abstract
- Light emitting diodes (LEDs) have become the most efficient artificial lighting source. Their application is found in general indoor and outdoor lighting, headlights in automobiles, and displays whether it be TVs, laptops, mobile phones or smart watches. This technology is enabled by III-V semiconductors. Standard LEDs are comprised of stacked layers where the active region in the form of multi quantum wells is sandwiched between the n- and p-doped layers. This architecture however has several constraints such as a limited light extraction efficiency because of the presence of contact pads at the top and bottom of the structure, and it suffers from the phenomenon of total internal reflection.
To address these challenges, this... (More) - Light emitting diodes (LEDs) have become the most efficient artificial lighting source. Their application is found in general indoor and outdoor lighting, headlights in automobiles, and displays whether it be TVs, laptops, mobile phones or smart watches. This technology is enabled by III-V semiconductors. Standard LEDs are comprised of stacked layers where the active region in the form of multi quantum wells is sandwiched between the n- and p-doped layers. This architecture however has several constraints such as a limited light extraction efficiency because of the presence of contact pads at the top and bottom of the structure, and it suffers from the phenomenon of total internal reflection.
To address these challenges, this thesis has presented a new architecture of LEDs implemented on nanowires. The structures resemble trees where the core nanowires of a high bandgap material provide the charge carriers, while the branches of a lower bandgap material act as the active region. Because of the difference in bandgap the carriers diffuse into the branches, where they recombine, and light is emitted. The dimension of the branches enables efficient light extraction overcoming total internal reflection.
In Paper I, the growth of nanotree structures is investigated by using a Au-containing solution to provide the seeds for branch growth. The successful growth of such structures is shown with a high density of branches.
In Paper II, the nanotree structures are processed into devices and a successful proof of concept of the diffusion of charge carriers from the cores to the branches is shown.
In Paper III, the structure is pushed one step further and doping is introduced in the branches and the devices are characterised to quantify its effect. The platform opens up a new window into alternative architectures for LEDs, which promise a high efficiency and low processing cost. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/045c42e2-0f1f-4076-a4b5-210755ac9bdf
- author
- Adham, Kristi LU
- supervisor
- organization
- publishing date
- 2024
- type
- Thesis
- publication status
- published
- subject
- keywords
- Nanowire, MOVPE, III-V semiconductor, light-emitting diodes, Fysicumarkivet A:2024: Adham
- pages
- 107 pages
- publisher
- Department of Physics, Lund University
- ISBN
- 978-91-8039-968-5
- 978-91-8039-969-2
- language
- English
- LU publication?
- yes
- additional info
- DDefence details Date: 2024-09-13 Time: 09:15 Place: Lecture Hall Rydbergsalen, Department of Physics, Sölvegatan 14C, Faculty of Engineering LTH, Lund University, Lund. External reviewer(s) Name: Oksanen, Jani Title: Sr Scientist. Affiliation: Aalto University, Finland.
- id
- 045c42e2-0f1f-4076-a4b5-210755ac9bdf
- date added to LUP
- 2024-07-05 13:45:59
- date last changed
- 2024-08-27 15:55:15
@phdthesis{045c42e2-0f1f-4076-a4b5-210755ac9bdf,
abstract = {{Light emitting diodes (LEDs) have become the most efficient artificial lighting source. Their application is found in general indoor and outdoor lighting, headlights in automobiles, and displays whether it be TVs, laptops, mobile phones or smart watches. This technology is enabled by III-V semiconductors. Standard LEDs are comprised of stacked layers where the active region in the form of multi quantum wells is sandwiched between the n- and p-doped layers. This architecture however has several constraints such as a limited light extraction efficiency because of the presence of contact pads at the top and bottom of the structure, and it suffers from the phenomenon of total internal reflection.<br/><br/>To address these challenges, this thesis has presented a new architecture of LEDs implemented on nanowires. The structures resemble trees where the core nanowires of a high bandgap material provide the charge carriers, while the branches of a lower bandgap material act as the active region. Because of the difference in bandgap the carriers diffuse into the branches, where they recombine, and light is emitted. The dimension of the branches enables efficient light extraction overcoming total internal reflection.<br/><br/>In Paper I, the growth of nanotree structures is investigated by using a Au-containing solution to provide the seeds for branch growth. The successful growth of such structures is shown with a high density of branches.<br/><br/>In Paper II, the nanotree structures are processed into devices and a successful proof of concept of the diffusion of charge carriers from the cores to the branches is shown.<br/><br/>In Paper III, the structure is pushed one step further and doping is introduced in the branches and the devices are characterised to quantify its effect. The platform opens up a new window into alternative architectures for LEDs, which promise a high efficiency and low processing cost.}},
author = {{Adham, Kristi}},
isbn = {{978-91-8039-968-5}},
keywords = {{Nanowire; MOVPE; III-V semiconductor; light-emitting diodes; Fysicumarkivet A:2024: Adham}},
language = {{eng}},
publisher = {{Department of Physics, Lund University}},
school = {{Lund University}},
title = {{Charge Carrier Diffusion Induced Light Emitting Diodes}},
url = {{https://lup.lub.lu.se/search/files/192194041/Kristi_e-nailing_Kappa.pdf}},
year = {{2024}},
}