The rapid expansion of AI data centers is changing the requirements for power semiconductor devices. Higher GPU power density, increasing rack power, and growing demand for efficient AC/DC and DC/DC conversion are accelerating the adoption of wide-bandgap semiconductors such as gallium nitride.

Among the different GaN platforms, GaN-on-silicon has attracted particular attention because it combines the electrical advantages of GaN with the manufacturing infrastructure of silicon wafers.

Today, 200mm GaN-on-Si wafers are already widely used for power and RF device development and manufacturing, while 300mm GaN-on-Si is increasingly being investigated as a potential route toward higher-volume production and deeper integration with mainstream semiconductor fabs.

However, moving from 200mm to 300mm is not simply a matter of increasing wafer diameter. Wafer bow, buffer-layer stress, epitaxy uniformity, defect control and fab compatibility all become more challenging.

This article explains the key differences between 200mm and 300mm GaN-on-Silicon wafers for AI power electronics.

Why GaN-on-Silicon Matters for AI Power Electronics

AI servers require multiple stages of power conversion.

Typical applications include:

• Data-center power supply units
• Server AC/DC converters
• 48V power architectures
• Intermediate bus converters
• High-frequency DC/DC converters
• Power delivery for GPUs and AI accelerators
• Telecom power systems
• Battery energy storage interfaces

GaN devices can operate at higher switching frequencies than conventional silicon MOSFETs, allowing smaller inductors, transformers and capacitors.

This can help improve:

• Power density
• Conversion efficiency
• System size
• Thermal performance
• Switching speed

GaN-on-Si is particularly attractive because silicon substrates are available in large diameters and are compatible with much of the equipment used in existing semiconductor manufacturing.

What Is a GaN-on-Silicon Wafer?

A GaN-on-Silicon wafer normally consists of several layers.

A simplified structure may include:

Silicon substrate
↓
Nucleation layer
↓
Stress-management or transition layers
↓
GaN buffer layer
↓
GaN channel layer
↓
AlGaN barrier or device epitaxy

The exact structure depends on the device application.

For GaN power electronics, the epitaxial stack may be optimized for:

• High breakdown voltage
• Low leakage current
• Low dynamic RDS(on)
• High electron mobility
• Low trapping
• High wafer uniformity

Because GaN and silicon have very different lattice constants and thermal expansion coefficients, sophisticated buffer structures are required.

These buffer layers become particularly important when wafer diameter increases.

200mm GaN-on-Si Wafers

200mm, or 8-inch, GaN-on-Silicon wafers have become an important platform for commercial GaN power device manufacturing.

The 200mm format offers a balance between manufacturing maturity and wafer-scale productivity.

Typical advantages include:

• Established 200mm silicon fab infrastructure
• Mature wafer handling equipment
• Lower development risk
• Easier wafer bow management
• Better established GaN epitaxy processes
• Lower initial equipment investment compared with 300mm

For many GaN device manufacturers, 200mm remains a practical choice for power devices targeting data centers, consumer power supplies, EV auxiliary systems and industrial power electronics.

Typical 200mm GaN-on-Si Parameters

Specifications depend on the epitaxial structure, but typical parameters may include:

Diameter: 200 mm

Substrate: Si (111)

Silicon thickness: approximately 725 µm

GaN epi thickness: application dependent

Conductivity: semi-insulating or device-specific buffer design

Surface: epi-ready or complete GaN epitaxy

Bow: controlled according to device process requirements

Warp: controlled for lithography and wafer handling

Surface roughness: typically sub-nanometer level for device-quality surfaces

Particle control: semiconductor-grade

For finished GaN epi wafers, additional parameters may include:

• Sheet resistance
• 2DEG density
• Electron mobility
• Buffer leakage
• Breakdown voltage
• Epitaxial thickness uniformity

Why the Industry Is Interested in 300mm GaN-on-Si

300mm wafers are standard in advanced silicon semiconductor manufacturing.

Moving GaN onto a 300mm platform could provide several long-term advantages.

The most important is manufacturing scale.

A 300mm wafer has significantly more usable area than a 200mm wafer, potentially allowing more devices to be fabricated per wafer.

For high-volume applications such as AI data-center power electronics, this may eventually improve manufacturing economics.

Other potential advantages include:

• Access to advanced 300mm fab infrastructure
• Higher automation levels
• More dies per wafer
• Better integration with CMOS manufacturing
• Compatibility with advanced packaging ecosystems
• Potential reduction in device cost at high production volume

However, these advantages are only meaningful if the GaN epitaxy can meet strict wafer-quality requirements.

That is the difficult part.

Wafer Bow: One of the Biggest 300mm Challenges

Wafer bow is one of the most important parameters when scaling GaN-on-Si from 200mm to 300mm.

GaN and silicon have very different lattice parameters and thermal expansion behavior.

During epitaxial growth at elevated temperature, mechanical stress builds inside the wafer.

After the wafer cools, this stress can cause the substrate to bend.

The larger the wafer diameter becomes, the more difficult stress control becomes.

Excessive bow can create problems during:

• Lithography
• Wafer chucking
• Spin coating
• Etching
• Ion implantation
• Metallization
• CMP
• Automated wafer handling

For 300mm GaN-on-Si, bow control becomes critical because modern semiconductor equipment is designed around strict wafer geometry limits.

A wafer that cannot sit correctly on a vacuum chuck may not be compatible with standard production equipment.

How Bow Is Controlled

GaN epitaxy suppliers use several techniques to manage stress.

These may include:

• AlN nucleation layers
• AlGaN transition layers
• Compositionally graded buffers
• Superlattice structures
• Carbon-doped GaN buffers
• Strain-compensation layers
• Optimized silicon substrate thickness

The design of the buffer stack directly influences both wafer geometry and electrical performance.

Buffer Layers Become More Important at 300mm

The buffer structure in GaN-on-Si is not simply a mechanical transition layer.

It also strongly affects device performance.

A properly designed buffer must provide:

• Stress compensation
• Electrical isolation
• Low leakage current
• High breakdown voltage
• Low dislocation density
• Low trapping
• Stable device performance

For high-voltage power devices, buffer leakage is particularly important.

A poor buffer design may result in:

• Premature breakdown
• Current collapse
• Increased leakage
• Dynamic RDS(on) degradation

When moving to 300mm, the buffer structure must remain uniform across a much larger wafer area.

This makes epitaxial process control significantly more demanding.

Epitaxy Uniformity: 200mm vs 300mm

Uniformity is another important difference.

For GaN power devices, the following properties should remain consistent across the wafer:

• GaN thickness
• AlGaN thickness
• Aluminum composition
• Sheet resistance
• Electron mobility
• 2DEG density
• Surface roughness
• Stress
• Defect density

On a 200mm wafer, achieving good center-to-edge uniformity is already challenging.

On a 300mm wafer, gas flow, temperature distribution and precursor delivery become more complicated.

Small temperature variations can affect:

• Growth rate
• Alloy composition
• Layer thickness
• Electrical properties

As a result, 300mm GaN epitaxy requires highly optimized MOCVD reactor design and process control.

Defect Density

GaN grown on silicon is a heteroepitaxial material system.

Threading dislocations are therefore unavoidable.

Typical defect types may include:

• Edge dislocations
• Screw dislocations
• Mixed dislocations
• Stacking faults
• Cracks
• Pits
• Particles

For power devices, these defects can influence:

• Leakage current
• Breakdown voltage
• Reliability
• Device yield

Scaling to 300mm makes wafer-level defect mapping increasingly important.

Advanced inspection systems may be used to monitor defect distribution across the entire wafer.

Cost Comparison

At first glance, 300mm appears more economical because more devices can be fabricated from each wafer.

However, wafer diameter alone does not determine total device cost.

Important cost factors include:

• Silicon substrate cost
• MOCVD growth time
• Epitaxy reactor utilization
• Wafer yield
• Device yield
• Lithography cost
• Inspection cost
• Equipment depreciation

Today, 200mm GaN-on-Si generally benefits from greater manufacturing maturity.

For lower and medium production volumes, 200mm may therefore remain more economical.

300mm becomes particularly attractive when production volume is high enough to take advantage of large-scale fab infrastructure.

Foundry Compatibility

One of the strongest reasons for developing 300mm GaN-on-Si is compatibility with silicon fabs.

However, a GaN wafer cannot automatically enter a standard silicon production line.

Several issues must be considered.

Wafer Geometry

The wafer must meet equipment requirements for:

• Diameter
• Thickness
• Bow
• Warp
• Edge profile

Contamination

GaN manufacturing introduces elements such as gallium and aluminum.

Silicon fabs often have strict contamination control rules.

Dedicated process modules or contamination-management strategies may therefore be required.

Thermal Budget

GaN epitaxy may involve high-temperature processes that differ from standard CMOS manufacturing.

Downstream processing must therefore be designed carefully.

Wafer Handling

Robot systems, FOUPs, aligners and lithography tools must correctly recognize and handle the wafer.

300mm GaN wafers must therefore follow very strict geometry and edge specifications.

200mm vs 300mm GaN-on-Si Comparison

200mm GaN-on-Si

Advantages:

• More mature manufacturing ecosystem
• Lower technical risk
• Established GaN power production
• Easier bow control
• Lower development cost

Best suited for:

• Commercial GaN power devices
• RF devices
• Data-center power supplies
• Fast chargers
• Industrial power electronics
• Automotive auxiliary systems

300mm GaN-on-Si

Advantages:

• More devices per wafer
• Advanced fab compatibility
• Higher automation potential
• Potential high-volume cost advantage
• Strong integration with advanced semiconductor manufacturing

Challenges:

• Wafer bow
• Stress control
• Epitaxy uniformity
• Defect management
• Contamination control
• Higher process-development complexity

Best suited for:

• Future high-volume GaN manufacturing
• AI data-center power electronics
• High-density power ICs
• Integrated power semiconductor platforms

What Parameters Should Buyers Specify?

When requesting GaN-on-Silicon wafers, buyers should provide more than wafer diameter.

Important RFQ parameters include:

Wafer Diameter

200mm or 300mm.

Silicon Orientation

Si (111) is commonly used for GaN epitaxy.

Wafer Thickness

Specify nominal thickness and tolerance.

GaN Structure

Specify whether you need:

• GaN template
• GaN epi wafer
• AlGaN/GaN HEMT structure
• High-voltage GaN power structure

Epitaxial Thickness

Specify required layer thicknesses.

Electrical Parameters

Depending on the device structure, specify:

• Sheet resistance
• Electron mobility
• Carrier concentration
• Leakage current

Wafer Geometry

Important parameters include:

• TTV
• Bow
• Warp

Surface Quality

Specify:

• Surface roughness
• Particle level
• Scratch requirements
• Edge exclusion

Defect Requirements

For advanced device manufacturing, wafer-level defect mapping may also be required.

Which Diameter Is Better for AI Power Electronics?

There is no universal answer.

For current GaN power device manufacturing, 200mm offers a mature and commercially practical platform.

For future high-volume AI power electronics, 300mm GaN-on-Si may offer important manufacturing advantages.

However, successful 300mm adoption depends on solving several materials and process challenges.

The most important include:

• Wafer bow control
• Stress engineering
• Uniform epitaxy
• Low-defect growth
• Electrical isolation
• Foundry compatibility

In many cases, epitaxial quality is more important than wafer diameter itself.

A poorly controlled 300mm wafer will not outperform a well-optimized 200mm GaN wafer simply because it is larger.

Conclusion

The transition from 200mm to 300mm GaN-on-Silicon represents an important step toward higher-volume GaN manufacturing.

For AI power electronics, the potential advantages are significant.

Larger wafers may enable more devices per wafer, improved fab automation and better integration with advanced semiconductor manufacturing infrastructure.

However, scaling GaN epitaxy to 300mm introduces major challenges in wafer bow, buffer-layer stress, epitaxy uniformity and defect control.

For device manufacturers and research institutes, wafer selection should therefore consider not only wafer diameter but also the complete epitaxial structure and wafer geometry.

For GaN-on-Silicon projects, buyers should provide detailed requirements including wafer size, silicon orientation, GaN structure, epitaxial thickness, bow, warp, electrical parameters and target device application.

A well-defined specification allows the GaN wafer structure to be optimized for the specific power device process and helps reduce development risk during wafer qualification and scale-up.