Industry Chain Deep Dive Series 1 of 'Vision Pocket Guide': The Origin of Light: Why Do the Three Primary Colors 'Go Their Separate Ways'?

Have you ever wondered where the gorgeous colors come from when a large LED screen lights up?

Red, green, and blue lights interweave the world in front of us, and behind these three lights, there are completely different materials science, process paths, and industrial games.

In 2026, "strengthening the chain, complementing the chain, and coordinating the entire chain" will continue to become the key words of China's display industry, and in-depth changes in the entire industry chain are taking place at all times. "Vision Tips" launches a new series to work with you through the complete journey from materials to modules, from chips to large screens, and jointly decode the "hard core insider knowledge" of the LED display industry.

In the first issue, we start with the three primary colors of light...

1. Why are they red, green, and blue? ——The "three primary color codes" of the human eye

The reason why humans can perceive the colorful world is due to the three types of photoreceptor cells on the retina. They are most sensitive to long wavelength, medium wavelength, and short wavelength light respectively. The brain synthesizes all the colors we see by analyzing the strength ratio of the signals received by these three types of cells.

This physiological characteristic determines that all modern display technologies - from CRT to LCD, from OLED to LED - follow the same underlying logic: using three primary colors of red, green and blue, mixed in different proportions, to simulate thousands of colors in nature. This is the ultimate source of the "three primary colors".

For LED displays, this means: we need semiconductor light-emitting devices that can efficiently emit red, green, and blue monochromatic light. However, different colors of light have completely different requirements for semiconductor materials - this is the fundamental reason why the LED industry chain bifurcated at the source.

2. Red light and blue-green light: two different technical routes

1. Red LED: aluminum gallium indium phosphorus system

The wavelength range of red light is about 620-750nm, and its luminescent core material is aluminum gallium indium phosphorus. This is a quaternary compound semiconductor obtained by epitaxial growth on a gallium arsenide substrate.

AET Altai whole industry chain·GaAs substrate

Why should AlGaInP be used for red light? AlGaInP is the preferred material for manufacturing high-brightness red LEDs. The core reason is that it has unique direct band gap, wavelength tunability, lattice matching and mass production comprehensive advantages in the red light band.

Process characteristics of red LED

●Use gallium arsenide substrate, usually 4-6 inches in diameter

●Epitaxial growth temperature is about 700-800℃

●The substrate is opaque, so red light chips usually adopt ① "reflective" structure to reflect downwardly emitted light upward; ② flip-chip structure to improve upward light extraction rate

●The technology matures early, but the substrate cost is high and the size is limited

2. Blue-green LED: Indium Gallium Nitride System

Blue light and green light come from another material system: Indium Gallium Nitride. This system is grown on a gallium nitride substrate or a heterogeneous substrate.

AET Altai's entire industry chain·Blue light chip

AET Altai's entire industry chain·Green light chip

Gallium nitride-based materials are a “rising star” in the LED field. In 1993, Shuji Nakamura successfully prepared a high-brightness blue LED on a sapphire substrate, making "full-color LED display" possible. Without blue light, it would be impossible to mix with red and green light to produce a complete color spectrum.

Process characteristics of blue-green LEDs

●The mainstream uses sapphire substrate, high-end uses silicon carbide, and the cost reduction direction uses silicon substrate

●The epitaxial growth temperature reaches 1000-1200°C, and the process is more difficult

●Green light is called the "efficiency gap" - its luminous efficiency is lower than red light and blue light, and it has gradually broken through in recent years

●The substrate is transparent, and the chip can be "formal" or "flip-chip"

3. Substrate Bifurcation: Industrial Mapping of Semiconductor Generations

Behind the above-mentioned differences in technical routes lies a deeper industrial logic: LED chips of different colors belong to different "generational" semiconductor material systems.

What is semiconductor generation?

The first generation of semiconductors

Represented by silicon and germanium, they are the cornerstones of integrated circuits, but their bandgaps are narrow and are not suitable for light-emitting devices.

Second generation semiconductors

Represented by gallium arsenide and indium phosphide, they have high electron mobility and are suitable for high-frequency and optoelectronic devices. Red LED is developed based on gallium arsenide substrate.

The third generation of semiconductors

Represented by gallium nitride and silicon carbide, they have characteristics such as wide bandgap, high breakdown electric field, and high thermal conductivity, and are suitable for high temperature, high frequency, high power and light-emitting devices. Blue-green LED is a typical application of the third generation semiconductor.

This "generational bifurcation" directly determines that the production line equipment, process parameters, and yield control strategies of LED chip manufacturing are completely different. This is why LED chip factories are usually divided into "red light production lines" and "blue-green light production lines" - they are like two parallel technological rivers, separated from the source, carrying different generations of semiconductor material systems.

4. Industrial bottleneck: from “three-color separation” to “full-color integration”

1. Green light dilemma: efficiency gap

Among the three RGB colors, green light has long been a "lag behind". Its luminous efficiency is significantly lower than red light and blue light. The reason is that in the InGaN material system, the growth window of the high-indium component is extremely narrow, which is prone to phase separation and defects, resulting in a decrease in internal quantum efficiency.

In recent years, by improving the epitaxial structure and optimizing the chip structure, the efficiency of green light has been significantly improved, but there is still a gap between it and red light and blue light. This bottleneck directly affects the power consumption and brightness level of the full-color display.

2. Changes in red light: from import dependence to domestic breakthrough

The gallium arsenide substrate used in red LEDs is a second-generation semiconductor that has long been highly dependent on imports. However, in recent years, the production capacity of domestic gallium arsenide substrate manufacturers has been rapidly released, the quality has continued to improve, and the localization rate has exceeded an important threshold. This breakthrough not only reduces the cost of red light chips, but also provides a solid guarantee for the security of the industrial chain and supply chain.

3. Micro LED full color: the ultimate challenge

When display technology moves towards the Micro LED era, a fundamental problem emerges: How to integrate millions of micron-level red, green, and blue chips on the same substrate? This is essentially a heterogeneous integration problem of second- and third-generation semiconductor materials.

The traditional method is "three-color independent transfer" - red light, blue and green light chips are prepared separately, and then placed on the drive backplane sequentially through mass transfer technology. However, this process is complex, has low yield and high cost.

Solutions being explored by the industry include:

Quantum dot color conversion

Preparing blue Micro LEDs in a unified manner, and then converting part of the blue light into red and green light through quantum dot materials

Monolithic integration

Growing red, green, and blue light-emitting layers on the same substrate to achieve "one chip emits three-color light"

Vertical stacking

Vertically stacking red, green, and blue chips to form full-color pixels

These cutting-edge explorations all point in the same direction: moving the three primary colors from "separation" to "integration", and moving the second and third generation semiconductors from "bifurcation" to "fusion." This is also a historic opportunity for China's LED display industry to move from "following" to "leading".

5. Value perspective for partners

By understanding the physical nature of the three primary colors, generational differences in semiconductors and industry bifurcation, you can answer more confidently when communicating with customers:

"Why are red light chips more expensive than blue light?"

Because red light uses a second-generation semiconductor gallium arsenide substrate, which has higher costs, limited size, and a more complex flip-chip structure of red light chips; blue light uses a third-generation semiconductor gallium nitride system, which has more obvious advantages in scale.

"Why are green LEDs low in efficiency?"

This is an inherent challenge of gallium nitride-based material systems, and epitaxial growth of high indium components is difficult. However, technology has made significant breakthroughs in recent years, and the green light efficiency of high-end products has been greatly improved.

“Why is Micro LED so difficult?”

Because it is necessary to achieve efficient integration and mass transfer of second- and third-generation semiconductor materials at the micron scale. This is not only a process issue, but also a systemic challenge in materials, equipment, and design.

"How is the progress of domestic substitution?"

The localization rate of second-generation gallium arsenide substrates has increased rapidly, third-generation gallium nitride substrates have become domestically produced, and silicon-based gallium nitride is accelerating to catch up - a pattern in which the entire industry chain is independent and controllable is taking shape.

6. Controlling color from the source: AET Altai’s entire industry chain layout

After understanding the technical logic of red light and blue-green light “going separate ways”, a more realistic question emerged: Who can truly open up these two roads and control the quality of color from the source?

The LED display industry chain has built a sophisticated technical chain from upstream to downstream: the upstream includes substrate preparation, epitaxial growth and chip manufacturing - this is the source of the highest technical barriers and determines the "gene" of the product. In this issue, we discuss "Why do the three primary colors go their own ways?" The root cause is precisely buried in the upstream substrate and chip links.

It is from this "source" that AET Altai relies on Guangdong Everbright Group's layout in the new optoelectronic display field to build independent capabilities covering the entire industry chain: from substrate to chip, controlling the "gene" of light.

Source of red light: Achieve large-scale production of 4-6-inch gallium arsenide substrates for optoelectronics, provide key support for high-end red LED devices, and ensure the efficiency and reliability of red light chips from the source.

The foundation of blue-green light: independently developed patterned sapphire substrate technology provides a high-quality substrate for the epitaxial growth of blue-green LEDs, effectively improves light extraction efficiency, and ensures luminescence consistency and yield from the source.

Next-generation core: Integrate MOCVD and HVPE dual technology routes to achieve mass production of 2-8-inch full-size gallium nitride single crystal substrates, with 8-inch product indicators leading the world; relying on independent epitaxial technology, focusing on the research and development of Mini/Micro LED chips, covering mainstream colors such as blue-green light and red light.

"Full-chain control" from the source allows AET Altai to have the ability to optimize quality from the origin of light emission at the beginning of product definition, truly realizing a closed loop of quality starting from the material end - every light-emitting chip originates from the same set of technical systems and the same set of quality control standards; every display screen carries the quality commitment from source to terminal.

As for the "intergenerational" battle behind different substrate materials - the technological evolution, size game and localization process of gallium arsenide and gallium nitride, we will go into depth in the next issue of "The Cornerstone of Light - The "Intergenerational" Battle of Substrate Materials".

"Vision Tips" industry chain in-depth series·next issue preview:

The cornerstone of light - the "intergenerational" battle for substrate materials

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