Why is the third-generation semiconductor so popular? 4 images to instantly understand GaN and SiC key technologies.

The third-generation semiconductor is currently the hottest topic in the high-tech field, playing an indispensable role in the development of 5G, electric vehicles, renewable energy, and Industry 4.0. Even though we often hear about these developments, many people still have only a vague understanding of them. So, what exactly is the third-generation semiconductor? In this series, we will provide the most straightforward and comprehensive perspective to help you understand this key technology that is poised to shape the future of the technology industry.

What is a third-generation semiconductor and wide-bandgap?

When we talk about third-generation semiconductors, let's first briefly introduce the first and second generations. In the field of semiconductor materials, the first-generation semiconductor is silicon (Si), and the second-generation semiconductor is gallium arsenide (GaAs). The third-generation semiconductor (also known as "wide-bandgap semiconductor," WBG) includes silicon carbide (SiC) and gallium nitride (GaN).

The "bandgap" in wide-bandgap semiconductors represents "the energy gap required for a semiconductor to transition from insulating to conducting states."

Silicon and gallium arsenide, as first and second-generation semiconductors, have low bandgaps, with values of 1.12 eV and 1.43 eV, respectively. In contrast, the bandgaps of third-generation (wide-bandgap) semiconductors SiC and GaN are 3.2eV and 3.4eV, respectively. Therefore, when subjected to high temperatures, pressures, or currents, third-generation semiconductors are less likely to transition from insulating to conducting states compared to the first and second generations. They exhibit more stable characteristics and better energy conversion capabilities.

Common misconceptions about third-generation semiconductors

With the advent of the 5G and electric vehicle era, the demand for high-frequency, high-speed computing, and fast charging has increased. Silicon and gallium arsenide have reached their limits in terms of temperature, frequency, and power, making it difficult to increase power and speed. Moreover, when operating temperatures exceed 100 degrees, the first two generations of products are more prone to failure, making them unsuitable for harsh environments. With the global focus on carbon emissions, high-efficiency, low-energy consumption third-generation semiconductors have become the new favorites of the era.

Third-generation semiconductors can maintain excellent performance and stability even at high frequencies. They also have characteristics such as fast switching speed, small size, and rapid heat dissipation. When chip sizes are greatly reduced, they help simplify peripheral circuit design, thereby reducing the volume of modules and cooling systems.

Many people mistakenly believe that third-generation semiconductors are accumulated from the technological advancements of the first and second generations, but this is not entirely true. As seen in the diagram, these three generations of semiconductors are actually developing technologies in parallel.

SiC and GaN each have their own advantages and different development areas.

After understanding the differences between the first three generations of semiconductors, we then focus on the materials of the third generation of semiconductors - SiC and GaN. These two materials have slightly different application areas. Currently, GaN components are commonly used in fields with voltages below 900V, such as chargers, base stations, and other high-frequency products related to 5G communications; SiC, on the other hand, is used in applications with voltages greater than 1200V, such as electric vehicles.

SiC is composed of silicon (Si) and carbon (C), with strong bonding and stability in terms of heat, chemistry, and mechanics. Due to its low loss and high power characteristics, SiC is suitable for high-voltage and high-current applications, such as electric vehicles, electric vehicle charging infrastructure, solar and offshore wind power generation equipment.

Furthermore, SiC itself uses "homogeneous epitaxy" technology, so it has good quality and high component reliability. This is also the main reason why electric vehicles choose to use it. Additionally, as it is a vertical device, it has high power density.

Currently, the power system of electric vehicles mainly operates between 200V and 450V, and higher-end models will move towards 800V in the future, making it the main market for SiC. However, SiC wafer manufacturing is difficult, with high requirements for the source crystal of the long crystal, which is not easily obtained. Moreover, the difficulty of long crystal technology means that large-scale production is still not feasible at present, which will be elaborated further later on.

GaN is a lateral component that grows on different substrates, such as SiC or Si substrates, using "heterogeneous epitaxy" technology. The GaN thin films produced by this method have relatively poor quality. Although they are currently used in consumer areas such as fast charging, there are some doubts about their use in electric vehicles or industrial applications, which is also a direction that manufacturers are eager to break through.

The application areas of GaN include high-voltage power devices (Power) and high-frequency components (RF). Power is often used as power converters and rectifiers, while commonly used technologies such as Bluetooth, Wi-Fi, and GPS positioning are examples of RF radio frequency components.

In terms of substrate technology, the production cost of GaN substrates is relatively high. Therefore, GaN components are mostly based on silicon substrates. The GaN power devices currently available on the market are manufactured using two types of wafers: GaN-on-Si (gallium nitride on silicon) and GaN-on-SiC (gallium nitride on silicon carbide).

Commonly heard GaN process technology applications, such as GaN RF radio frequency devices and PowerGaN, are derived from GaN-on-Si substrate technology. As for GaN-on-SiC substrate technology, due to the difficulties in manufacturing silicon carbide substrates (SiC), the technology is mainly controlled by a few international manufacturers, such as Cree and II-VI in the United States, and ROHM Semiconductor.