Single crystals are rare in nature, and even when they do occur, they are usually very small—typically on the millimeter (mm) scale—and difficult to obtain. Reported diamonds, emeralds, agates, etc., generally do not enter market circulation, let alone industrial applications; most are displayed in museums for exhibition. However, some single crystals hold significant industrial value, such as single-crystal silicon in the integrated circuit industry, sapphire commonly used in optical lenses, and silicon carbide, which is gaining momentum in third-generation semiconductors. The ability to mass-produce these single crystals industrially not only represents strength in industrial and scientific technology but is also a symbol of wealth. The primary requirement for single crystal production in the industry is large size, as this is key to reducing costs more effectively. Below are some commonly encountered single crystals on the market:
1. Sapphire Single Crystal
Sapphire single crystal refers to α-Al₂O₃, which has a hexagonal crystal system, a Mohs hardness of 9, and stable chemical properties. It is insoluble in acidic or alkaline corrosive liquids, resistant to high temperatures, and exhibits excellent light transmission, thermal conductivity, and electrical insulation.
If Al ions in the crystal are replaced by Ti and Fe ions, the crystal appears blue and is called sapphire. If replaced by Cr ions, it appears red and is called ruby. However, industrial sapphire is pure α-Al₂O₃, colorless and transparent, without impurities.
Industrial sapphire typically takes the form of wafers, 400–700 μm thick and 4–8 inches in diameter. These are known as wafers and are cut from crystal ingots. Shown below is a freshly pulled ingot from a single crystal furnace, not yet polished or cut.
In 2018, Jinghui Electronic Company in Inner Mongolia successfully grew the world’s largest 450 kg ultra-large-size sapphire crystal. The previous largest sapphire crystal globally was a 350 kg crystal produced in Russia. As seen in the image, this crystal has a regular shape, is fully transparent, free of cracks and grain boundaries, and has few bubbles.
2. Single-Crystal Silicon
Currently, single-crystal silicon used for integrated circuit chips has a purity of 99.9999999% to 99.999999999% (9–11 nines), and a 420 kg silicon ingot must maintain a diamond-like perfect structure. In nature, even a one-carat (200 mg) diamond is relatively rare.
Global production of single-crystal silicon ingots is dominated by five major companies: Japan’s Shin-Etsu (28.0%), Japan’s SUMCO (21.9%), Taiwan’s GlobalWafers (15.1%), South Korea’s SK Siltron (11.6%), and Germany’s Siltronic (11.3%). Even the largest semiconductor wafer manufacturer in mainland China, NSIG, holds only about 2.3% of the market share. Nevertheless, as a newcomer, its potential should not be underestimated. In 2024, NSIG plans to invest in a project to upgrade 300 mm silicon wafer production for integrated circuits, with an estimated total investment of ¥13.2 billion.
As the raw material for chips, high-purity single-crystal silicon ingots are evolving from 6-inch to 12-inch diameters. Leading international chip foundries, such as TSMC and GlobalFoundries, are making chips from 12-inch silicon wafers the market mainstream, while 8-inch wafers are gradually being phased out. Domestic leader SMIC still primarily uses 6-inch wafers. Currently, only Japan’s SUMCO can produce high-purity 12-inch wafer substrates.
3. Gallium Arsenide
Gallium arsenide (GaAs) wafers are an important semiconductor material, and their size is a critical parameter in the preparation process.
Currently, GaAs wafers are typically produced in sizes of 2 inches, 3 inches, 4 inches, 6 inches, 8 inches, and 12 inches. Among these, 6-inch wafers are one of the most widely used specifications.
The maximum diameter of single crystals grown by the Horizontal Bridgman (HB) method is generally 3 inches, while the Liquid-Encapsulated Czochralski (LEC) method can produce single crystals up to 12 inches in diameter. However, LEC growth requires high equipment costs and yields crystals with non-uniformity and high dislocation density. The Vertical Gradient Freeze (VGF) and Vertical Bridgman (VB) methods can currently produce single crystals up to 8 inches in diameter, with relatively uniform structure and lower dislocation density.
Production technology for 4-inch and 6-inch semi-insulating GaAs polished wafers is primarily mastered by three companies: Japan’s Sumitomo Electric Industries, Germany’s Freiberger Compound Materials, and the U.S.’s AXT. By 2015, 6-inch substrates already accounted for over 90% of the market share.
In 2019, the global GaAs substrate market was dominated by Freiberger, Sumitomo, and Beijing Tongmei, with market shares of 28%, 21%, and 13%, respectively. According to estimates by consulting firm Yole, global sales of GaAs substrates (converted to 2-inch equivalents) reached approximately 20 million pieces in 2019 and are projected to exceed 35 million pieces by 2025. The global GaAs substrate market was valued at around $200 million in 2019 and is expected to reach $348 million by 2025, with a compound annual growth rate (CAGR) of 9.67% from 2019 to 2025.
4. Silicon Carbide Single Crystal
Currently, the market can fully support the growth of 2-inch and 3-inch diameter silicon carbide (SiC) single crystals. Many companies have reported successful growth of 4-inch 4H-type SiC single crystals, marking China’s achievement of world-class levels in SiC crystal growth technology. However, there is still a significant gap before commercialization.
Generally, SiC ingots grown by liquid-phase methods are relatively small, with thicknesses at the centimeter level. This is also a reason for the high cost of SiC wafers.
XKH specializes in the R&D and customized processing of core semiconductor materials, including sapphire, silicon carbide (SiC), silicon wafers, and ceramics, covering the full value chain from crystal growth to precision machining. Leveraging integrated industrial capabilities, we provide high-performance sapphire wafers, silicon carbide substrates, and ultra-high-purity silicon wafers, supported by tailored solutions such as custom cutting, surface coating, and complex geometry fabrication to meet extreme environmental demands in laser systems, semiconductor fabrication, and renewable energy applications.
Adhering to quality standards, our products feature micron-level precision, >1500°C thermal stability, and superior corrosion resistance, ensuring reliability in harsh operating conditions. Additionally, we supply quartz substrates, metal/non-metallic materials, and other semiconductor-grade components, enabling seamless transitions from prototyping to mass production for clients across industries.
Post time: Aug-29-2025