Have you heard of Gallium Nitride (GaN)? This compound semiconductor is known for its superior performance compared to silicon, particularly in high-voltage, high-temperature, and high-current applications. GaN's attributes make it ideal for high-frequency and lightweight electronic products, which are critical in fields like 5G/6G communications, drones, autonomous vehicles, and radar systems. As a result, GaN has become a hot topic in research and development over the past decade, with Taiwan being no exception. Professor Chang Yi, Dean of the International Semiconductor Industry Research Institute at National Yang Ming Chiao Tung University, has been at the forefront of GaN device and process research. To advance Taiwan's integration and technology in this area, he has sought out the "best partners" through journal publications and initiated a collaborative effort with a German team.

 

Professor Chang Yi has been exploring semiconductor materials for over 30 years and is a pioneer in Taiwan's compound semiconductor industry. His early work involved achieving the world’s highest frequency of 780 GHz with Gallium Arsenide. With the rise of GaN as a key semiconductor material, Professor Chang shifted his focus to this area.

 

Recalling his collaboration with Germany, Professor Chang said, "I discovered through journal papers that the Ferdinand-Braun-Institut (FBH) in Germany not only had a strong foundation in high-frequency IC design but also had rich experience in packaging. At that time, Taiwan lacked talent and resources in this field, so I decided to reach out to them, expressing my interest in visiting Berlin. I happened to be bringing PhD students to the European Microwave Conference in Munich, and they generously welcomed us." Packaging is a crucial aspect of semiconductor design and manufacturing; it impacts power consumption, performance, and cost from a macro perspective, and involves the basic functions of the chip from a micro perspective. Packaging can be thought of as the "container" for semiconductor chips, requiring consideration of how to protect the chip, connect it to the circuit board, and achieve high-frequency and thermal management.

 

This decision opened the door for Professor Chang to years of international collaboration. He believes Taiwan can leverage its advantages in semiconductor device processing to learn from FBH's expertise in high-frequency packaging and design, benefiting system integration. Additionally, he notes that the tight collaboration within the European Union provides Taiwan with opportunities to access a broader range of technological resources.

 

Many people may not be familiar with GaN, a significant third-generation semiconductor material. Professor Chang explains that GaN features a wide bandgap, high electron mobility, and high breakdown voltage. "I realized early on that the U.S. military had begun transitioning all GaAs development to GaN, so I quickly entered this field."

 

Recently, Professor Chang and his team have utilized Metal-Organic Chemical Vapor Deposition (MOCVD) to grow GaN single crystals on silicon or silicon carbide substrates, a process known as epitaxy. They have also incorporated quantum wells into GaN materials. This special structure, with high energy levels on the sides and lower energy levels in the middle, allows for the confinement of electrons in the middle region, enhancing device performance by reducing collisions with other ions. "Unlike silicon, GaN’s surface has many energy levels that can automatically release electrons without doping. Typically, semiconductors need doping to conduct current, but GaN generates significant current through its surface dangling bonds," Professor Chang elaborates.

 

GaN technology was initially valued in military applications due to its high power density, enabling the miniaturization of radar systems and extending communication ranges for drones, enhancing the capabilities of smart warfare equipment.

 

Beyond military uses, GaN also plays a crucial role in civilian applications, especially in communications infrastructure. GaN RF components are essential for high-speed, high-data-rate, and low-latency communications. "For example, in broadcasting live Olympic events, GaN technology ensures real-time and clear transmission to large screens at the venue," Professor Chang notes. He also mentions the importance of GaN in autonomous vehicles, which require rapid data transmission systems to make real-time decisions. "If data transmission is slow or insufficient, autonomous vehicles could face collisions or fail to make timely maneuvers."

 

In addition to high-frequency applications, GaN is also a significant player in energy efficiency, especially in RF power amplifiers. These devices amplify weak RF signals to a high power state, enabling long-distance transmission with minimal distortion and noise. This efficiency benefits various applications, from radio broadcasting to medical devices.

 

Taiwan's interaction with AI companies like NVIDIA also involves GaN technology. Professor Chang highlights, "AI and semiconductor integration demand extensive computation, which is energy-intensive. Data centers using GaN materials could save enough electricity to power a nuclear plant." However, he notes that this has not yet been realized because AI data centers currently do not use that much power. "If there are many data centers, the government might need to mandate energy-saving practices to mitigate environmental impacts."

 

Professor Chang uses smartphones as an example: "Modern iPhones don’t include chargers, and chargers with low efficiency are not used. This creates an opportunity for GaN to be more energy-efficient." For telecom operators, using substandard transistors and ICs can lead to excessive noise and high energy consumption, compromising system performance. "If telecom companies enforce standards for energy efficiency and quality, GaN technology will have significant prospects."

 

To enable large-scale industrial application of GaN technology, breakthroughs in process technology are crucial. Professor Chang emphasizes that government policies encouraging the adoption of GaN-based high-efficiency power sources could accelerate the industrialization process.

 

He reiterates the importance of GaN in communication systems: "For communication systems to meet future demands, integrating components effectively is key. Understanding how components emit signals, minimize interference, and manage signal purity is crucial to overall design and manufacturing." Professor Chang believes that with a solid theoretical foundation, Taiwan has the potential to excel in these areas.

 

Additionally, linking domestic and international academic and research resources to strengthen the entire supply chain from materials to components and systems will be vital. "In Taiwan, semiconductors are our strength, and developing the entire industry chain is feasible." Professor Chang’s team is already collaborating with top international universities, such as Nagoya University in Japan for high-frequency, high-power transistors, and UCLA in the U.S. for high-frequency circuit design.

 

"Each country has its strengths, and each university’s resources are limited. We may excel in one aspect, but integrating packaging, IC design, and system components requires collaboration. By combining existing strengths with our research, we can accelerate core technological breakthroughs and enhance Taiwan’s international influence in GaN."

 

With its combination of high-frequency capabilities, durability, energy efficiency, and data transmission speed, GaN is rapidly penetrating our daily lives and is poised to play a crucial role in next-generation communications. We look forward to ongoing breakthroughs in GaN technology to create more efficient and energy-saving innovations.

 

Notes:
[1] The first generation of semiconductors includes silicon and germanium, the second generation includes GaAs and InP, and the third generation includes SiC and GaN.

 

Source: Interview with Dr. Zhang Yi, Dean of the International College of Semiconductor Technology at National Yang Ming Chiao Tung University

※ This article is reprinted from 'Science and Technology Vista', originally titled 'From Military Applications to Solving AI Computational Energy Consumption Problems: How Compound Semiconductor 'Gallium Nitride' is Opening the Door to Next-Generation Communications and Applications.

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