Advances in Light Emitting Diodes: A
Comprehensive Review
Aryan Aich, Aditya Doke
Electronics and Telecommunications
Dept.
JSPM’s RSCOE
Tathawade, Pune
Abstract— Light emitting diodes (LEDs) have become a companies developed the first high-brightness LEDs, which
popular source of lighting in recent years due to their high were capable of emitting visible light. These LEDs were used
efficiency and long lifespan. This paper provides an overview of primarily in niche applications, such as traffic signals and
the science behind LED technology, including the basic automotive lighting. In the 1990s, the development of new
principles of operation and the materials used to create LEDs.
materials, such as indium gallium nitride (InGaN), led to
It also discusses the advantages and challenges of using LEDs
for lighting applications, including their energy efficiency, significant improvements in LED efficiency and output,
durability, and ability to produce a wide range of colors. The paving the way for their widespread adoption in lighting and
paper reviews recent advances in LED technology, such as the display applications.
development of high-power LEDs and the use of nanotechnology
to enhance LED performance. Finally, the paper examines the c) Introduction of white LEDs (1990s-2000s): Prior
environmental impact of LED lighting and considers the to the 1990s, LEDs were primarily used for single-color
potential for LEDs to help reduce energy consumption and applications, such as red or green indicator lights. In the
greenhouse gas emissions. 1990s, researchers developed the first blue LEDs, which
Keywords— semiconductor, doping, LED, lighting,
enabled the creation of white LEDs through the combination
decoration, reliability, durability. of blue light with phosphors. This breakthrough paved the
way for the use of LEDs in general lighting applications, and
I. INTRODUCTION led to the development of new lighting technologies, such as
The development of light emitting diodes (LEDs) has LED-based light bulbs.
revolutionized the lighting industry over the past few
decades. First discovered in the 1920s, LEDs were initially d) Continued advancements in performance and
used only in niche applications due to their limited light efficiency (2000s-present): In the past two decades,
output and high cost. However, advances in materials science researchers and manufacturers have continued to make
and semiconductor technology have led to significant significant advancements in LED performance and
improvements in LED performance and efficiency, resulting efficiency. This includes the development of new materials
in their widespread adoption for a variety of lighting and structures, such as quantum dots and nanowires, as well
applications. as improvements in manufacturing processes and packaging
technologies. These advancements have enabled the creation
Today, LEDs are used not only for lighting but also in a of high-performance and cost-effective LEDs for a wide
range of other applications, from displays and signage to range of applications, from automotive and medical devices
automotive lighting and horticulture. This paper provides an to horticultural lighting and architectural lighting.
overview of the history and evolution of LED technology, III. MANUFACTURING PROCESS OF AN LED
from its discovery to its current state-of-the-art applications.
The manufacturing process of an LED typically involves
several steps, including:
II. EVOLUTION OF LIGHT EMITTING DIODES
The evolution of LEDs has been driven by advancements in 1) Substrate preparation: A substrate material, such
materials science, semiconductor technology, and as a sapphire or silicon wafer, is prepared for use in the LED
manufacturing processes. Here's a brief overview of some fabrication process. This may involve cleaning, polishing,
key milestones in the evolution of LEDs: and/or coating the substrate to ensure that it is free of
impurities and has the desired properties.
a) Discovery and early development (1920s-1960s):
The first LED was invented in 1927 by Oleg Vladimirovich 2) Epitaxy: The substrate is then coated with a thin
Losev, a Russian inventor. However, early LEDs were low in layer of semiconductor material, typically Gallium Nitride
efficiency and were only able to emit infrared light. In the (GaN) or a related compound. This process, known as
1960s, researchers at General Electric and other companies epitaxy, involves heating the substrate and introducing gases
made significant progress in improving the efficiency and containing the desired semiconductor material, which then
output of LEDs, leading to their first practical applications in condense onto the substrate to form a thin film.
electronic displays and indicator lights.
3) Doping: The semiconductor layer is then doped
b) Development of high-brightness LEDs (1970s- with impurities to create regions of p-type and n-type
1990s): In the 1970s, researchers at Monsanto and other material. This is typically done using a process called ion
implantation or diffusion, which introduces specific efficiency. LEDs use far less energy to produce the same
impurities, such as magnesium or silicon, into the amount of light, which can result in significant cost savings
semiconductor material to create regions with excess or and environmental benefits. In addition, LEDs have a much
deficient electrons. longer lifespan than traditional bulbs, with some models
capable of lasting up to 50,000 hours or more. This means
4) Metal contacts: Metal contacts are added to the p- that LEDs require less frequent replacement, reducing
type and n-type regions to allow electrical current to flow maintenance costs and waste. However, while LEDs have
through the LED. This is typically done using a process called many benefits, there are also challenges associated with their
deposition, which involves depositing a thin layer of metal, use, such as high initial cost and potential issues with color
such as gold or aluminum, onto the surface of the LED. rendering and dimming. This paper will explore both the
advantages and challenges of using LEDs for lighting
5) Etching and patterning: The LED is then etched applications and provide insight into the current state of LED
and patterned to create the desired shape and size. This technology.
involves using chemicals to selectively remove material from
the LED, leaving behind the desired pattern.
VI. COLOR RANGES OF LEDS AND THEIR SEMICONDUCTOR
6) Packaging: Finally, the LED is packaged into a MATERIALS
housing or module, which may include additional
components such as a lens or reflector to help direct the light. The range of colors that can be obtained by an LED depends
The packaging process also typically involves attaching wires on the materials used in its construction. LEDs are typically
or leads to the metal contacts to allow the LED to be made from semiconductor materials such as gallium arsenide
connected to a power source. (GaAs), gallium nitride (GaN), or indium gallium nitride
(InGaN), which emit light of different wavelengths when a
Overall, the manufacturing process for LEDs is highly current is passed through them.
specialized and requires expertise in materials science,
semiconductor physics, and manufacturing engineering. By varying the composition of the semiconductor
Advances in LED manufacturing technology have enabled material, the wavelength of light emitted by an LED can be
the development of high-performance and cost-effective controlled, allowing for the creation of LEDs that emit
LEDs for a wide range of applications, from lighting and different colors of light. For example:
displays to automotive and medical devices.
1) Red LEDs: typically made from aluminum gallium
arsenide (AlGaAs) or gallium arsenide phosphide (GaAsP),
IV. FUNCTIONING OF AN LED which emit light in the red wavelength range (around 630-
In order to understand how LEDs work, it is important to 660 nanometers).
consider their underlying physical properties.
LEDs are nothing but are among the siblings of the Diode 2) Green LEDs: typically made from gallium
family. Their characteristics of functionality are no different phosphide (GaP) or aluminum gallium indium phosphide
than a Diode. The only difference lies in the miscellaneous (AlGaInP), which emit light in the green wavelength range
property of this particular type of Diode (LED) to emit Light. (around 520-570 nanometers).
LEDs are a type of semiconductor device that converts
electrical energy into light. 3) Blue LEDs: typically made from indium gallium
nitride (InGaN), which emit light in the blue wavelength
When an electrical current is applied to the range (around 450-470 nanometers).
semiconductor material, electrons are excited and jump from
the lower energy valence band to the higher energy 4) White LEDs: typically made by combining a blue
conduction band. As the electrons return to their original LED with a yellow phosphor coating, which produces a broad
energy state, they release energy in the form of photons, spectrum of light that appears white to the human eye.
producing light. The wavelength of the emitted light is
determined by the energy difference between the valence and Characteristics of Different Colored LEDs
conduction bands, which can be tuned by adjusting the Dominant
Forward Voltage
Wavelength
chemical composition and structure of the semiconductor LED Color
Min Typ Min Typ
material.
Red 2.1 2.4 620 630
The VI characteristics of an LED vary according to the
Yellow 2.1 2.4 580 590
Substrates used in it for the emission of a variety of Light
colors. The VI characteristics graphs for the same are given Green 3.4 2.4 520 530
at the end of the Sixth Section. (VI. COLOR RANGES OF
Blue 3.4 2.4 460 465
LEDS AND THEIR SEMICONDUCTOR MATERIALS)
White 3.4 2.4 6000 6500
V. ADVANTAGES OF LIGHT EMITTING DIODES
One of the key advantages of LEDs over traditional
incandescent or fluorescent lighting is their energy
In addition to these standard colors, LEDs can also be made
in a range of other colors, such as yellow, orange, and purple, 3) Automotive lighting: LEDs are used in a variety of
by using different combinations of materials and controlling automotive lighting applications, including headlights,
the manufacturing process. taillights, and interior lighting. They offer improved energy
efficiency, durability, and brightness compared to traditional
Notice that the White LED has a staggering increase in halogen or incandescent bulbs.
Wavelength as compared to other wavelengths, this is because
the White light comprises of most of the light waves.
Below are the V-I Characteristics of various types of LEDs 4) Signage: LEDs are used extensively in signage
based on their colour: applications, such as illuminated signs and channel letters.
They offer bright, vibrant colors and can be used to create a
wide range of effects.
5) Consumer electronics: LEDs are used in a variety
of consumer electronics products, including cameras, gaming
devices, and remote controls. They offer low power
consumption and can be used to create backlit buttons and
displays.
6) Medical devices: LEDs are used in medical devices
for a variety of purposes, including surgical lighting,
phototherapy, and diagnostics. They offer improved energy
efficiency, precision, and safety compared to traditional
lighting technologies.
7) Aerospace and defense: LEDs are used in
aerospace and defense applications, such as aircraft lighting
and guidance systems, due to their durability and reliability
in harsh environments.
Fig. 1. V-I Characteristics of various LED Color types.
Overall, the versatility and flexibility of LEDs have enabled
The above graph shows the different cut-in voltages
their use in a wide range of applications, and they continue to
required by each LED. This is useful for knowing what the
be a popular choice for new and emerging technologies.
minimum required voltage is for operating a chosen LED
with a specific colour. ACKNOWLEDGMENTS
VII. APPLICATIONS OF LIGHT EMITTING DIODES Aryan Aich has the credit for all the documentation and
preparation of this document and ensuring that the document
LEDs have become increasingly popular in a wide range of meets the IEEE standards.
applications due to their energy efficiency, long lifespan,
durability, and versatility. Here are some common Aditya Doke reserves the credit for all the researching and
applications of LEDs: information collection, and final editing of the document such
as error-proofing, grammar and making sure the document
does not contain words which are iteratively used.
1) Lighting: LEDs are widely used in general lighting
applications, including residential and commercial lighting, REFERENCES
street lighting, and architectural lighting. They are also used [1] "HJ Round was a pioneer in the development of the LED".
in specialized lighting applications, such as horticultural www.myledpassion.com. Archived from the original on October 28,
lighting and UV disinfection. 2020. Retrieved April 11, 2017.
[2] "Semiconductor Radiant Diode", James R. Biard and Gary Pittman,
2) Displays: LEDs are commonly used in electronic Filed on Aug. 8th, 1962, Issued on Dec. 20th, 1966.
displays, such as smartphones, TVs, and digital billboards. [3] "Inventor of Long-Lasting, Low-Heat Light Source Awarded $500,000
Lemelson-MIT Prize for Invention". Washington, D.C. Massachusetts
They are also used in smaller displays, such as those found in Institute of Technology. April 21, 2004.
automotive dashboards and appliances.
