Silicon carbide (SiC) has emerged as one of the most promising wide-bandgap semiconductors, and among its polytypes, 6H-SiC holds a special place thanks to its balance of properties and established growth technology. Within 6H-SiC substrates, two types exist based on doping: N-type and P-type. This article provides a comparative analysis of the two, from their definitions and properties to their advantages, applications, and development trends.

I. Definition

6H-SiC: A hexagonal polytype of SiC with a crystal structure repeating every six layers and a bandgap of ~3.0 eV.
6H-N-type SiC substrate: Doped with nitrogen (N), with electrons as majority carriers.
6H-P-type SiC substrate: Doped with aluminum (Al) or boron (B), with holes as majority carriers.

 

II. Properties Comparison

 

Feature	6H-N-type	6H-P-type
Dopant	Nitrogen (N)	Aluminum (Al), Boron (B)
Conductivity	N-type (electrons)	P-type (holes)
Resistivity	Low (0.02–0.5 Ω·cm)	Higher (0.5–tens of Ω·cm)
Bandgap	~3.0 eV	~3.0 eV
Thermal conductivity	3–4.9 W/cm·K	3–4.9 W/cm·K
Crystal structure	Hexagonal	Hexagonal

 

III. Advantages

6H-N-type:
Low resistivity, ideal for epitaxial growth.
Mature processing and established supply chain.
Excellent for high-power, high-voltage devices.
6H-P-type:
Enables PN junction formation for diodes.
Useful in optoelectronics and sensor applications.
Provides diversity in device architecture.

IV. Applications

6H-N-type substrates:
Power devices: MOSFETs, Schottky diodes, IGBTs.
RF and high-frequency switching devices.
Electronics in harsh environments (high temperature, radiation).
6H-P-type substrates:
Research and epitaxy of P-type layers.
Optoelectronic devices: UV detectors, LEDs.
Special power devices using PN junctions or symmetric structures.

V. Development Trends

N-type dominance: The commercial power device industry overwhelmingly uses N-type 6H/4H-SiC substrates.
P-type niche: P-type is mainly used in research and specialized devices due to its higher resistivity and growth challenges.
Scaling up: From 2-inch to 4-inch and 6-inch wafers, with ongoing progress toward 8-inch.
Improved quality: Reducing dislocation density and enhancing epitaxial quality remain central goals.
Complementary role: Future device landscapes may see 6H-SiC substrates (N and P) working alongside 4H-SiC for a diverse range of power and optoelectronic applications.

 

VI. Summary Table

Aspect	6H-N-type	6H-P-type
Role in industry	Mainstream, widely used	Specialized, research-focused
Strength	Low resistivity, high-power devices	PN junction formation, optoelectronics
Limitation	Less suited for P-layer research	Higher resistivity, lower adoption
Market outlook	Strong and growing	Niche, but important for innovation

 

Conclusion

6H-N-type SiC substrates have become the backbone of the SiC power electronics industry, powering high-voltage MOSFETs, diodes, and IGBTs. In contrast, 6H-P-type substrates remain a niche but valuable material for research, optoelectronics, and PN junction-based devices. Together, they form a complementary ecosystem that will continue to evolve as wafer sizes scale, defect densities fall, and demand for high-performance semiconductors accelerates.
In the long run, the synergy of N-type and P-type 6H-SiC will help push the boundaries of power electronics, optoelectronics, and beyond.