In the world of advanced materials and microelectronics, sapphire wafers have become increasingly significant due to their exceptional physical, chemical, and optical properties. Whether used in LED manufacturing, semiconductor substrates , or optical applications, sapphire wafers offer a wide range of benefits that make them ideal for high-performance and high-reliability technologies.
What Is a Sapphire Wafer?
A sapphire wafer is a thin slice of single-crystal aluminum oxide (Al₂O₃), also known as synthetic sapphire. It is produced through crystal growth techniques such as the Kyropoulos or Czochralski method, and then sliced and polished into wafers of varying thicknesses and diameters.
Key Properties of Sapphire Wafers
Crystal Structure: Hexagonal Lattice Constant (nm): a=4.76Å c=12.99A Density (g/cm3): 3.98 Melting point (℃): 2040 Mohs Hardness (mohs): 9 Dielectric Constant: 9.3 (A plane)/11.5 (C plane) Thermal Conductivity (W/cm.K): 0.46 Thermal Expansion: 6.7*10-6/k(C plane) 5.0*10-6/k(A plane) Refractive Index: 1.762-1.777
Specification of sapphire substrates
Diameter：25.4mm/50.8mm/76.2mm/100mm/150mm/200mm Thickness: 430μm/650μm/800μm/1000μm Surface Orientation: C-plane (0001) off-angle toward M-axis(10-10) 0.2 ± 0.1° Primary Flat Orientation: A-Plane (11-20) ± 1.0° Primary Flat Length: 8mm/16mm/22mm/30mm/47.5mm/Notch Front Surface Finish: Si-Face: CMP, Ra<0.3nm Back Surface Finish: C-Face: SSP: Fine-ground, Ra=0.8-1.2μm; DSP: Epi-polished, Ra<0.3nm Laser Mark: Back side TTV: 5-30μm BOW: 8-40μm WARP:10-60μm
Advantages of Using Sapphire Wafers
1. Ideal Substrate for GaN and LED Devices
One of the primary uses of sapphire wafers is as a substrate for gallium nitride (GaN) epitaxy in blue and white LEDs. The lattice structure of sapphire is well-matched to GaN, enabling efficient light emission and reliable device performance.
2. Superior Surface Quality
Sapphire wafers can be polished to atomic-level smoothness, minimizing defects and enhancing the performance of epitaxial layers grown on them.
3. High Yield and Scalability
With advancements in crystal growth and wafering technologies, sapphire wafers are now available in larger diameters (up to 8 inch sapphire substrate ), supporting scalable manufacturing and high-volume production.
4. Biocompatibility
Due to its inert and biocompatible nature, sapphire is used in medical implants and biosensing devices.
5. Resistance to Radiation
Sapphire retains its optical and mechanical properties even under high radiation exposure, making it suitable for space and nuclear applications.
Applications of Sapphire Wafers
LED and laser diode substrates Optical windows and lenses Semiconductor substrates (especially for RF and power devices) Watch crystals and durable screens Biomedical sensors and implants Aerospace and defense components
Conclusion
Sapphire wafers stand out in today's high-tech landscape for their unmatched durability, thermal and chemical resistance, and optical clarity. As technology continues to push the limits of performance and miniaturization, sapphire will remain a key material in enabling next-generation electronic and optical devices. 
