Evolution of LED Chip Technology: Efficiency and Cost Game from Blue Light Revolution to Micro LED

Keywords: LED chip, blue LED, Micro LED, epitaxial growth, quantum efficiency

abstract

LED chips are the core of lighting and display technology. This article analyzes the technological evolution and commercialization path of Micro LED from epitaxial growth, quantum efficiency improvement to industrialization.

1.1 Technological breakthroughs in blue LED

InGaN material system: In 1993, Shuji Nakamura's team achieved mass production of blue LED by doping p-type GaN with Mg, with a light efficiency exceeding 100lm/W (white LED efficiency increased to 200lm/W).

MOCVD epitaxial process: The Aixtron G5+reactor can simultaneously grow 24 4-inch wafers at a growth rate of 3 μ m/h and a defect density of<10 ⁸ cm ⁻ 2.

1.2 Key Technologies for Efficiency Improvement

Graphic sapphire substrate (PSS): By dry etching, periodic conical structures are formed, reducing the dislocation density of epitaxial layers by 50% and increasing the light extraction efficiency by 30%.

Electron Barrier Layer (EBL): Adopting AlGaN/GaN superlattice structure, it suppresses electron leakage and increases the Internal Quantum Efficiency (IQE) from 70% to 90%.

1.3 Industrialization challenges of Micro LED

Large scale transfer technology: ASM Pacific's laser lift off (LLO) and pick&place equipment can transfer 100000 chips per hour (with an accuracy of ± 1 μ m), but the yield rate is only 85%.

Full color scheme: Quantum Dot Color Conversion (QDCC) technology excites red/green quantum dots through blue light, with a color gamut coverage of 95% of Rec. 2020, but needs to address the issue of photoluminescence efficiency degradation (efficiency drops by 40% at 85 ℃).

1.4 Cost optimization path

Silicon based LED: By utilizing CMOS process compatibility, a single-chip integrated driver circuit is achieved, with chip size reduced to 50 μ m × 50 μ m and cost reduced to $0.01/mm 2.

Vertical structure chip: The sapphire substrate is removed by laser exfoliation, and a Cu metal bonding layer is used to reduce the thermal resistance to 5K/W (traditional horizontal structure is 15K/W).

1.5 Standardization and Testing Certification

IES LM-80 standard: requires LED light sources to maintain a luminous flux maintenance rate of>91.8% after 6000 hours of aging (L70 lifespan>50000 hours).

LM-79 report: Using an integrating sphere testing system, measure luminous flux (unit: lm), luminous efficiency (lm/W), and color rendering index (CRI>80).

conclusion

Micro LED is the mainstream direction for next-generation display and lighting, but it needs to solve the problems of high transfer yield and full-color efficiency. Through material innovation and process optimization, a balance between efficiency and cost can be achieved.