4H-SiC and 6H-SiC: Their Difference and Selection Guide

Silicon carbide material is amongst the most commonly used for semiconductor manufacturing and new energy sources. 4H-SiC and 6H-SiC possess the same chemical structure. But their different atomic structures lead to completely different performance. Knowing these differences is critical for optimizing your industrial cost and efficiency.

This article will introduce properties and applications in industry of both polytypes to help you select the ideal one for your specific high-performance requirements.

Crystal Structures of Silicon Carbide β-phase (Left) α-phase (Right)

Table of Contents

Structural Differences of Silicon Carbide Polytypes

4H-SiC and 6H-SiC are 2 different types of silicon carbide ceramic materials. Their chemical compositions are the same. The difference lies in the stacking sequence of atoms. This microscopic structural variance is the reason for their differences in performance, processing stability, and application scenarios between the two.

The atomic arrangement of 4H-SiC is more regular and uniform, leading to more stable performance. During processing, production, and practical application, 4H-SiC is less likely to experience performance fluctuations. This makes it better for meeting the demands of large-scale mass production.

In contrast, the atomic arrangement of 6H-SiC is relatively more complex, which causes its performance to be more significantly influenced by the orientation of use. Its stability is slightly inferior to that of 4H-SiC.

These differences in composition will influence the performance of silicon carbide materials. In the following sections, we will explain the characteristics and applications of 4H-SiC and 6H-SiC materials, and we will then set a clearer range according to your industrial choice.

4H-SiC – Properties and Applications

Because of ordered atomic structure, 4H-SiC exhibits superior thermal conductivity, high breakdown voltage, and minimal high-frequency loss. Its low defect density provides the stability that is required for mass production of high-precision components.

Moreover, with energy losses only 1/10 those of silicon, 4H-SiC offers a significant efficiency advantage. It serves as the primary substrate for power devices in strategic sectors like new energy and industrial control.

New Energy Vehicles: When used in on-board chargers and motor drive systems, 4H-SiC MOSFETs can reduce power loss by 47% and decrease the volume of cooling systems by 60%, indirectly extending vehicle range by 5% to 10%. Leading automakers, for example, Tesla and BYD, have employed 4H-SiC MOSFETs.

Photovoltaics: 4H-SiC inverters can boost the conversion efficiency to 99% and even more. An 100MW photovoltaic power station can generate additional 960,000 kWh of electricity every year, lowering the levelized cost of energy.

Communications: 4H-SiC can be applied in 5G base station RF parts and industrial high-voltage frequency converters.

6H-SiC – Properties and Applications

6H-SiC possesses lower electron mobility limits its use in high-end power electronics compared to 4H-SiC. But its excellent photoelectric conversion efficiency makes it a necessity for customied UV detectors and high-temperature optoelectronics.

Besides, its ability to be synthesized from recycled wind turbine blades offers a sustainable, cost-effective solution. Constrained by greater crystal growth difficulty and higher defect rates, the scope of large-scale commercial application for 6H-SiC remains far more limited than that of 4H-SiC.

Optoelectronics: 6H-SiC served as the core material for early blue LEDs and UV detectors. It is suitable for the R&D of customized high-temperature resistant SiC optoelectronic devices, still irreplaceable in specific photoelectric applications.

Industrial Settings: 6H-SiC is utilized to manufacture high-temperature sensors and small-scale kiln components that do not demand extreme high-frequency performance. 6H-SiC is fully capable of meeting fundamental operational requirements.

Mechanical Applications: Excellent wear and corrosion resistance, as well as high fracture toughness of 6H-SiC, make it ideal for mechanical applications. Mechanical parts such as cutting tools and bearings benefit from the durability and stress resistance offered by 6H-SiC.

Comparison Between 4H-SiC and 6H-SiC

The table below details the specific performance metrics of 4H-SiC and 6H-SiC. You can review it quickly to understand their specific capabilities.

Parameter	4H-SiC	6H-SiC
Stacking Sequence	4-layer periodicity	6-layer periodicity
Bandgap	3.26 eV	3.02 eV
Electron Mobility	~900 cm²/V·s (High & nearly isotropic)	~400 cm²/V·s (Lower & highly anisotropic)
Thermal Conductivity	~4.5 W/cm·K	~3.0 – 4.5 W/cm·K
Core Advantages	l Superior Electrical Performance l Low on-resistance	l Mature Growth Process l Lower cost

Selection Guide Between 4H-SiC and 6H-SiC: Which One is More Suitable?

Material selection lies in matching your specific production scenarios, mass-production planning, and cost budget. Avoid blindly chasing higher technical parameters. You may follow these two principles.

Prioritize 4H-SiC if your industrial focus is on high efficiency, and large-scale mass production is required. Its mature manufacturing processes and stable performance effectively reduce risks in component R&D and mass production while meeting the demands of high-voltage platforms. Moreover, it creates higher economic value by reducing energy loss and enhancing efficiency.

Choose 6H-SiC when you are handling customized optoelectronics. Its wider bandgap and special crystalline structure provide transparency in the visible light spectrum, ideal for specialized LED and sensor substrate applications. If you are worried about a limited budget or environmental sustainability, 6H-SiC is also a good choice. For extreme temperatures and mechanical wear, 6H-SiC is also available due to its excellent mechanical properties.

The table below lists the applications of 4H-SiC and 6H-SiC. You can use the information below to judge which is better for your application.

Field	4H-SiC	6H-SiC
Power Electronics	Electric Vehicles (Inverters), Fast Chargers, Photovoltaic Inverters.	Rarely used for power switches; used in basic industrial components.
RF / Wireless	GaN-on-SiC for 5G Base Stations	RF substrate
Optoelectronics	Limited use	LED Substrate (Blue/Green LEDs), UV photodetectors
Other Fields	High-performance & high-temp electronics	Abrasives, refractory materials, high-temp pressure sensors
Market Status	The industry standard for power semiconductors	Focused on LEDs and specific research

Conclusion

Learning the differences of 4H-SiC and 6H-SiC is important for you to select the most suitable silicon carbide material for your industrial application. 4H-SiC plays a major role in the field of power devices. 6H-SiC continues to find its place, leveraging its photoelectric characteristics and environmentally friendly advantages.

By making your choice closely with your specific requirements, you can maximize the value of silicon carbide ceramic materials. Newthink New Materials provides a range of SiC polytypes products to help engineers and researchers select the most suitable one for their projects. Feel free to contact us to get further information.

Thanks for your reading. Hope this article is helpful.

FAQs

What is 4H-SiC and 6H-SiC?

They are the two most common polytypes of silicon carbide ceramic materials. They have the same chemical structure with different atomic arrangements.

What is the difference between 4H and 6H?

The main difference is the stacking sequence of atoms. 4H-SiC has higher electron mobility and stability, ideal for power electronics. 6H-SiC is better for optoelectronics and mechanical parts.

What are the properties of 6H-SiC?

6H-SiC is known for its excellent photoelectric conversion, high mechanical hardness, wear resistance, and the ability to be produced by eco-friendly recycling processes.