As third-generation semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN) continue to gain traction in high-power electronic applications, researchers are actively exploring the next generation of wide-bandgap semiconductors. Among these, gallium oxide (Ga₂O₃) has emerged as a promising candidate due to its ultra-wide bandgap (4.8–5.3 eV) and exceptionally high breakdown electric field (>8 MV/cm). The successful fabrication of 4-inch and larger Ga₂O₃ single crystals has further accelerated its industrial development.

This article discusses the growth methods of 4-inch Ga₂O₃ single crystals, key material properties, application prospects, and current challenges in commercialization.

1. Why Is Gallium Oxide (Ga₂O₃) Gaining Attention?

Gallium oxide (Ga₂O₃) is an emerging ultra-wide bandgap semiconductor that surpasses conventional silicon (Si) and third-generation semiconductors (SiC and GaN) in terms of bandgap energy and breakdown electric field.

As shown in the table, Ga₂O₃ exhibits a significantly higher breakdown electric field than SiC and GaN, making it particularly advantageous for high-power and high-voltage device applications.

Moreover, unlike SiC and GaN, which require expensive epitaxial growth techniques due to their high melting points, Ga₂O₃ can be grown via melt-based methods, reducing production costs and facilitating large-scale manufacturing.

2. Growth Techniques for 4-Inch Ga₂O₃ Single Crystals

The successful commercialization of Ga₂O₃ relies heavily on the ability to fabricate high-quality, large-diameter single crystals. The main growth techniques include:

(1) Vertical Bridgman (VB) Method

This method involves melting Ga₂O₃ source material in a crucible and gradually cooling it to promote crystallization. It enables the growth of large-diameter, low-defect Ga₂O₃ crystals and is well-suited for mass production.

(2) Floating Zone (FZ) Method

The FZ method utilizes induction heating to melt the source material without a crucible, followed by controlled crystallization. This technique produces high-purity, low-defect Ga₂O₃, but its scalability for large-diameter wafers is limited due to gravitational constraints.

(3) Edge-Defined Film-Fed Growth (EFG) Method

EFG leverages capillary action to draw molten Ga₂O₃ upward through a die, where it crystallizes into a large-area wafer. This technique enables the direct fabrication of thin, large-diameter Ga₂O₃ substrates, making it suitable for 4-inch and larger wafer production.

(4) Physical Vapor Transport (PVT) Method

PVT involves sublimating Ga₂O₃ source material at high temperatures and allowing it to condense and crystallize in a lower-temperature region. While this method produces high-quality β-Ga₂O₃ single crystals, its relatively slow growth rate poses challenges for large-scale wafer production.

3. Key Properties of 4-Inch Ga₂O₃ Single Crystals

The performance of 4-inch Ga₂O₃ wafers is crucial for their application in high-power electronic devices. The following table summarizes key material properties:

Ga₂O₃ can be effectively n-type doped using Sn or Si, allowing for tunable electrical conductivity. However, achieving stable p-type doping remains a major challenge, limiting the development of complementary metal-oxide-semiconductor (CMOS) circuits.

4. Applications of 4-Inch Ga₂O₃ Single Crystals

Thanks to its unique material properties, Ga₂O₃ demonstrates enormous potential in the following fields:

(1) High-Power Electronic Devices

Ga₂O₃’s high breakdown field makes it ideal for power switching devices, such as metal-oxide-semiconductor field-effect transistors (MOSFETs) and Schottky barrier diodes (SBDs). Compared to SiC and GaN, Ga₂O₃ enables higher power densities with smaller device footprints.

(2) Deep-Ultraviolet (DUV) Photodetectors

With its ultra-wide bandgap, Ga₂O₃ is highly transparent in the ultraviolet range, making it suitable for solar-blind DUV photodetectors (250–280 nm). These devices are essential in fire detection, environmental monitoring, and biological sensing.

(3) Radio Frequency (RF) and Microwave Devices

Ga₂O₃ is promising for high-frequency applications, such as 5G communication and millimeter-wave radar, where it can be used in power amplifiers and low-loss RF switches.

(4) Transparent Electronics

The optical transparency of Ga₂O₃ makes it an excellent candidate for transparent conductive films, optoelectronic devices, and integrated optical circuits.

5. Challenges and Future Development Trends

Despite its promising potential, Ga₂O₃ faces several challenges that must be addressed before widespread commercialization:

• p-Type Doping Limitations: Achieving stable and efficient p-type doping remains a significant obstacle, limiting Ga₂O₃’s applicability in CMOS-compatible circuits.

• Uniformity Control for Large-Diameter Wafers: Maintaining crystal quality and uniform electrical properties across 6-inch and larger Ga₂O₃ wafers is critical for industrial-scale adoption.

• Thermal Management Issues: Ga₂O₃ has relatively low thermal conductivity (10–27 W/m·K), necessitating advanced heat dissipation strategies, such as integration with high-thermal-conductivity materials like SiC or diamond.

6. Conclusion

The successful growth and application of 4-inch Ga₂O₃ single crystals are driving significant advancements in next-generation power electronics. With ongoing improvements in crystal growth techniques and device fabrication processes, Ga₂O₃ is poised to play a transformative role in high-voltage power electronics, wireless communications, and deep-ultraviolet detection. As the semiconductor industry continues to innovate, Ga₂O₃ could become a key material for future high-performance electronic and optoelectronic devices.