Sapphire substrates are opening new possibilities for advanced power semiconductor manufacturing.

On October 13, 2026, Japanese semiconductor technology company FLOSFIA announced that it had successfully deposited alpha-phase gallium oxide (α-Ga₂O₃) epitaxial layers on 6-inch sapphire substrates.

Using its proprietary Mist Dry deposition technology, the company achieved approximately ±3% in-plane film thickness variation, meeting its initial target of no more than ±4%.

The announcement represents an important development for large-diameter gallium oxide epitaxy and highlights the potential of sapphire as a substrate material for emerging wide-bandgap semiconductors.

Why Alpha-Ga₂O₃ Is Attracting Attention

Gallium oxide is being investigated as a semiconductor material for next-generation power electronic devices.

Its potential advantages include a very wide bandgap and a high theoretical critical electric field.

These properties make gallium oxide an interesting candidate for power devices requiring high blocking voltages.

However, practical semiconductor applications depend on overcoming several challenges, including thermal management, material defects, contact formation, device stability, and scalable manufacturing.

Different crystalline phases of gallium oxide also have different structural and electronic properties.

Alpha-phase gallium oxide has a corundum crystal structure that makes sapphire a particularly interesting substrate for heteroepitaxial growth.

Why Sapphire Is Suitable for Alpha-Ga₂O₃ Epitaxy

Sapphire is a single-crystal form of aluminum oxide (Al₂O₃).

It is widely used in semiconductor and optoelectronic manufacturing, particularly for LED-related applications.

Its advantages include excellent chemical stability, mechanical hardness, high-temperature resistance, and established crystal manufacturing technology.

Importantly, sapphire and α-Ga₂O₃ share a corundum-type crystal structure.

This structural relationship enables the investigation and development of alpha-phase gallium oxide epitaxy on sapphire substrates.

Nevertheless, lattice mismatch and differences in thermal properties remain important considerations.

Suitable epitaxial growth conditions and defect management are required to obtain high-quality semiconductor films.

Why the Transition to 6-Inch Sapphire Matters

Increasing substrate diameter is one of the main approaches used to improve the economics of semiconductor manufacturing.

A 6-inch wafer provides approximately 2.25 times the nominal surface area of a 4-inch wafer.

This larger area creates the potential for more semiconductor devices per wafer, assuming suitable process uniformity and manufacturing yield.

For emerging semiconductor materials, access to larger substrates may also improve compatibility with existing manufacturing equipment.

FLOSFIA's October 2026 announcement is especially relevant because it demonstrates epitaxial deposition on a 150mm sapphire wafer.

The company also indicated that its results support further work toward 200mm sapphire processing.

However, successful deposition on 150mm wafers should not be interpreted as proof that 200mm production has already been fully established.

Additional process development and manufacturing qualification remain necessary.

Thickness Uniformity Is a Key Epitaxial Parameter

For semiconductor epitaxial layers, thickness uniformity is an important quality characteristic.

Variations in film thickness can influence process consistency and, depending on the device structure, electrical performance.

Achieving stable deposition across a larger wafer requires careful control of precursor delivery, chemical reactions, temperature, and other process conditions.

FLOSFIA reported approximately ±3% in-plane thickness variation for its 6-inch α-Ga₂O₃ epitaxial film.

This result indicates progress in large-area process uniformity.

However, complete epitaxial layer evaluation also requires additional parameters, such as crystal structure, defect density, surface morphology, and electrical properties.

Thickness uniformity is therefore an important achievement, but not the sole criterion for determining device readiness.

Sapphire Substrate Specifications for Epitaxial Growth

For companies developing gallium oxide or other semiconductor layers on sapphire, substrate selection requires careful attention.

Several technical specifications should be considered.

1. Crystal Orientation

Sapphire wafers can be manufactured in different crystallographic orientations, including C-plane, A-plane, R-plane, and M-plane.

The appropriate orientation depends on the desired epitaxial structure and growth process.

C-plane sapphire is frequently studied for corundum-phase epitaxial materials, but customers should confirm the exact orientation required by their process.

2. Surface Roughness

The polished surface should be suitable for epitaxial growth.

Surface roughness is commonly characterized by atomic force microscopy.

Buyers should specify the required roughness parameter, scan area, and measurement method.

3. Total Thickness Variation

TTV describes the difference between maximum and minimum wafer thickness.

Appropriate thickness control helps maintain consistent wafer positioning and process compatibility.

4. Bow and Warp

Wafer shape is especially important when moving toward larger substrate diameters.

Excessive bow or warp can create difficulties in automated handling, substrate contact, and semiconductor processing.

5. Surface Defects

Scratches, pits, contamination, and polishing damage can influence epitaxial growth.

Epi-ready sapphire substrates generally require carefully controlled polishing, cleaning, and inspection processes.

6. Substrate Thickness

The substrate thickness must be compatible with the deposition equipment and any subsequent thinning or device fabrication steps.

Different research systems and production platforms may require different thickness specifications.

The Importance of Epi-Ready Sapphire Wafers

An epi-ready sapphire wafer is manufactured with surface conditions intended to support subsequent epitaxial deposition.

Producing these substrates typically involves crystal slicing, precision grinding, lapping, polishing, cleaning, and quality inspection.

For semiconductor applications, double-side-polished (DSP) sapphire wafers may be preferred when processing or inspection requires high-quality surfaces on both sides.

Single-side-polished (SSP) wafers may also be appropriate depending on the fabrication process.

The correct choice depends on equipment requirements rather than a universal preference for one polishing configuration.

For α-Ga₂O₃ growth, users should confirm whether the proposed sapphire substrate has been qualified under their specific epitaxial conditions.

Sapphire Wafers for Emerging Semiconductor Applications

The development of larger-diameter gallium oxide epitaxy may create new opportunities for the sapphire substrate industry.

Potential application areas include:

• Alpha-Ga₂O₃ epitaxial research

• Wide-bandgap power semiconductor development

• Experimental high-voltage devices

• Semiconductor heteroepitaxy

• Advanced thin-film research

• New oxide semiconductor processes

Sapphire already benefits from established manufacturing capabilities developed for optical and LED applications.

This existing supply base may help researchers access material in different diameters and surface grades.

However, requirements for advanced power semiconductor epitaxy may differ substantially from those used in conventional LED manufacturing.

Material specifications should therefore be determined according to the actual epitaxial process.

What Buyers Should Confirm Before Ordering

For 6-inch sapphire wafers intended for semiconductor research or production, buyers should provide a complete technical specification.

Important purchasing details include:

• Wafer diameter: 150mm class

• Required crystal orientation

• Orientation tolerance and offcut

• Nominal wafer thickness

• Thickness tolerance

• TTV, bow, and warp requirements

• SSP or DSP surface preparation

• Surface roughness specification

• Flat or notch requirements

• Cleaning and packaging conditions

• Required quantity and inspection documentation

If the sapphire will be used for α-Ga₂O₃ epitaxy, the growth method and thermal processing conditions should also be communicated to the substrate supplier.

Providing these details during the initial inquiry can help reduce specification misunderstandings and improve material selection.

From 6-Inch to 8-Inch Sapphire Epitaxy

One important aspect of FLOSFIA's announcement is its longer-term interest in 8-inch sapphire-based epitaxial processing.

The company reported that experimental results from smaller wafer diameters supported a projected thickness variation within ±4% at 200mm.

This projection is encouraging, but it remains distinct from a completed 200mm manufacturing demonstration.

The transition will require continued optimization of deposition uniformity, substrate handling, film quality, and manufacturing repeatability.

Nevertheless, the development suggests that sapphire could become an increasingly relevant substrate for emerging oxide semiconductor technologies.

Conclusion

The successful deposition of α-Ga₂O₃ epitaxial layers on 6-inch sapphire wafers represents a noteworthy step in the development of next-generation power semiconductor materials.

For sapphire wafer manufacturers and buyers, the significance extends beyond a single experimental result.

The development demonstrates the importance of large-diameter sapphire substrates with controlled crystal orientation, high-quality polished surfaces, and reliable wafer geometry.

As gallium oxide semiconductor research advances, the demand for precisely specified sapphire substrates may expand into new applications beyond conventional optics and LED manufacturing.

Careful substrate selection and cooperation between wafer suppliers and epitaxial technology developers will be essential to supporting future progress.