Application of SiC materials in AR glasses

Abstracts:

As augmented reality (AR) glasses move toward higher performance and miniaturization, the demand for advanced substrate materials has never been greater. This article explores the role of semi-insulating silicon carbide (SiC) substrates in enabling high-resolution, thermally stable Micro-LED displays used in AR systems. It highlights the structural characteristics of SI-SiC, such as ultra-high resistivity, excellent thermal conductivity, and compatibility with GaN epitaxy.

AR glasses industry background:

AR glasses are the perfect carrier for AI applications, which can combine virtual and reality. AR glasses (augmented reality glasses) are a kind of smart wearable device that superimposes virtual information on the real world. The core lies in the perfect integration of virtual information and the real world. In 2024, the global shipment of AR glasses reached 553,000 pairs, a year-on-year increase of 7.8%, of which China shipped 286,000 pairs in 2024. The optical display system is the core of AR glasses. The optical display system consists of an optical combiner and a micro display screen. The optical display system is the core component of the entire AR glasses and the component with the largest value, accounting for about 40%+ of the cost of the entire AR glasses.

The surface relief grating waveguide solution is the future mainstream trend of the optical display system of AR glasses. The surface relief grating waveguide has relatively controllable manufacturing costs, mature processes, and excellent optical performance. Although there are dispersion and rainbow pattern problems, the substrate can be replaced with SiC to solve them. Combining the technical level and the difficulty of mass production, surface relief grating waveguide is the most realistic and promising mass production solution. The mainstream AR glasses that are about to be launched all adopt this solution.

Performance advantages of silicon carbide materials:

Silicon carbide materials have high refractive index and high thermal conductivity, making them ideal substrate materials for AR glasses lenses. The higher the refractive index of the substrate material, the larger the FOV of the AR lens. A single-layer SiC lens can achieve a FOV of more than 80 degrees, which can provide a lighter and thinner size and a larger and clearer visual effect. High refractive index can also effectively solve the rainbow pattern and dispersion problems in the optical waveguide structure. High thermal conductivity effectively improves the heat dissipation capacity and performance of AR glasses. At the same time, the high hardness and thermal stability of SiC materials also support the introduction of etching processes, effectively improving production capacity and yield.

1. Structural and performance characteristics of semi-insulating SiC substrate:

Semi-insulating SiC is a silicon carbide material with extremely high resistivity (usually > 1×10⁸ Ω·cm), mainly based on 4H or 6H crystal forms. By introducing deep energy level impurities (such as vanadium, chromium, etc.) or controlling intrinsic defects, it has nearly insulating electrical properties.

2. Its key structural and performance advantages include:

● High resistivity characteristics: effectively suppress parasitic current and leakage, suitable for high-frequency and high-voltage application environments.

Excellent thermal conductivity: The thermal conductivity can reach 3~4.9 W/cm·K, which is better than most semiconductor materials and supports stable operation of devices.

● High breakdown electric field strength: about 3 MV/cm, which is more than 10 times that of silicon, improving the reliability and integration density of power devices.

● Good crystal integrity and size controllability: suitable for manufacturing high-quality micro-display devices (such as Micro-LED or VCSEL epitaxial growth substrates).

SiC+SRG optical waveguide+etching process is the technical basis for the significant progress of AR glasses. Silicon carbide materials with high refractive index and high thermal conductivity and surface relief grating waveguides effectively improve the FOV of AR glasses, solve the existing rainbow patterns, dispersion and light loss, and achieve lightweight design and good passive heat dissipation. The development of silicon carbide substrates, surface relief grating waveguides, and breakthroughs in etching processes are the technical basis for the future acceleration of product improvement and mass shipment of AR glasses in the consumer market.

AR glasses lenses require semi-insulating silicon carbide substrates, and large-size substrates are the key to cost reduction. Large-size substrates can significantly reduce cutting losses and thus reduce lens material costs. Only by breaking through the mass production process of 12-inch substrates can the cost of silicon carbide substrates be reduced, driving AR glasses into the mass consumer market.

3. Advantages of semi-insulating SiC substrates in AR:

In AR glasses, semi-insulating SiC substrates are mainly used as Micro-LED epitaxial growth substrates or high-frequency electronic device substrates. Their core functions include:

✔Suppressing leakage current and improving image signal purity.

✔Improving device thermal stability and extending service life.

✔Compatible with gallium nitride (GaN) epitaxial system and supporting high-brightness Micro-LED development.

✔Supporting stable operation of high-frequency and high-speed driver chips and improving response speed.

As AR glasses develop towards lighter, smarter and higher-definition directions, higher requirements are placed on the stability and energy efficiency of display chips, and semi-insulating SiC substrates are the key basic materials supporting this development.