Will gallium nitride (GaN) become the next outlet in the market?

With the upgrading of consumer electronics, electric vehicles, household appliances and other products, more and more attention is paid to the performance of products, especially in terms of power design. How to improve the energy efficiency of power conversion, increase the power density level, and extend the battery life has become the biggest challenge facing the new generation of electronic products.

In this context, the emergence of a new type of power semiconductor-Gallium Nitride (GaN), may become the future of the electronics industry.

GaN, which has been dormant for 20 years, was "accidentally" made popular by Lei Jun

At the Xiaomi Mi 10 press conference that just ended last month, it became popular with Mi 10, and Lei Jun, the founder of Xiaomi, focused on introducing the 65W Mi GaN charger. Lei Jun praised it as "it's so convenient!" While the new products became popular, they also attracted wide attention from investors to the third-generation semiconductors.

Before understanding GaN, we must first figure out some knowledge about semiconductor materials. The development of semiconductor materials has now entered the third generation.

The first-generation semiconductor materials mainly refer to materials of elements such as silicon (Si) and germanium (Ge), which are commonly used in discrete devices and integrated circuits in information technology; in computers, mobile phones, televisions, aerospace, various military projects, etc. It has been widely used in the industry.

The second-generation semiconductor materials mainly refer to compound semiconductor materials, such as gallium arsenide (GaAs) and indium antimonide (InSb); ternary compound semiconductors, such as GaAsAl, GaAsP; and some solid solution semiconductors, such as Ge-Si, GaAs- GaP; glass semiconductors (also called amorphous semiconductors), such as amorphous silicon, glassy oxide semiconductors; and organic semiconductors, such as phthalocyanine, copper phthalocyanine, polyacrylonitrile, etc. It is mainly used to make high-speed, high-frequency, high-power and light-emitting electronic devices. It is an excellent material for making high-performance microwave, millimeter wave devices and light-emitting devices.

The third-generation semiconductor materials are mainly wide-gap semiconductor materials represented by silicon carbide (SiC), gallium nitride (GaN), zinc oxide (ZnO), diamond, and aluminum nitride (AlN). In terms of application, according to the development of third-generation semiconductors, its main applications are semiconductor lighting, power electronic devices, lasers and detectors, and four other fields.

In 1998, the United States developed a GaN transistor. According to data, GaN has a band gap of 3.49 eV (electron volts) at room temperature. Generally speaking, the band gap refers to the forbidden band width, which is an important characteristic parameter of semiconductor materials, and its size is mainly determined by the energy band structure of the semiconductor.

Because wide bandgap semiconductor materials have the characteristics of large forbidden band width, high breakdown electric field strength, high saturated electron drift speed, large thermal conductivity, small dielectric constant, strong radiation resistance and good chemical stability, they are very suitable for producing anti-radiation, high frequency, high power and high density integrated electronic devices.

Take GaN as an example, its melting point is as high as 1700°C. Someone has done experiments, under normal high temperature conditions, GaN will not undergo decomposition reaction. GaN will slowly volatilize only when it is placed in nitrogen or helium and the temperature exceeds 1000°C, proving that GaN can maintain its stability at higher temperatures. This is why GaN can be widely used in high-power semiconductors.

GaN industry chain and application prospects

Similar to the SiC industry chain, the GaN industry chain can be divided into GaN substrate → GaN epitaxy → device design → device manufacturing. From the perspective of the development of the GaN industry at home and abroad, the United States and Japan have become the leaders in the development of the GaN industry, while Chinese companies have entered the game.

Fast charging product field: GaN material has a wide range of applications, and the most well-known is in the fast charging product field. When the fast charge first appeared, everyone was not optimistic about it. I always felt that a battery was fully charged in such a short period of time, and I was worried that the battery would explode. With the gradual upgrade of fast charging to super fast charging, the charging time is getting shorter and shorter. Although the hidden worry about battery safety has not been completely put down, people are more and more willing to accept it.

Compared with traditional fast charging, the new GaN fast charge provides higher energy conversion efficiency due to the material characteristics of GaN, reduces power consumption, and reduces heating problems during charging; GaN chargers have greater power density, A faster charging speed can be achieved; in addition, the switching frequency of the GaN charger power device is significantly higher than that of the Si power device in the traditional fast charging, so a smaller charger product design can be realized.

5G RF field: With the explosion of 5G technology, the requirements of related industries for RF power and power consumption have further increased, and GaN will gradually replace Si materials. In militarized scenarios such as phased array radar, electronic countermeasure warfare, and precision guidance, GaN is also used more and more widely.

Market research and strategy consulting company Yole once stated that the GaN radio frequency device market reached US$457 million in 2018, with a compound growth rate of over 23% in the next five years. In the entire RF application market, the market share of GaN devices will gradually increase. In the long run, in the field of macro base stations and backhaul, relying on the performance advantages of high frequency and high power, GaN will gradually replace LDMOS and GaAs to occupy the dominant position.

Electric vehicles, photovoltaics and other power semiconductor fields: IGBTs currently used in electric vehicles, photovoltaics, smart grids and other fields are silicon-based materials. If gallium nitride technology makes a breakthrough in the future and penetrates into the IGBT semiconductor field, gallium nitride will be further opened. The ceiling of the market.

Lighting field: Semiconductor lighting is a new type of high-efficiency, energy-saving and environmentally friendly light source that has attracted much attention at home and abroad. It will replace most of the traditional light sources and is also known as the energy revolution of the 21st century. GaN can be inter-doped with NIn and NAl to change the proportion of group III elements, so that its emission wavelength can cover the range from red light to ultraviolet light, thereby achieving higher efficiency and high brightness light source applications.

What are the disadvantages?

Although GaN is more energy-efficient, faster and has better recovery characteristics than Si and other materials, it is still not a complete replacement. For several reasons, GaN is not often used in transistors. GaN devices are usually depletion-type devices. They will turn on when the gate-source voltage is zero. This is a problem.

Secondly, the polarity of GaN devices is too large to obtain better metal-semiconductor ohmic contact through high doping. This is a difficult problem in the manufacture of GaN devices. The best solution now is to use heterojunctions. The forbidden band width gradually transitions to a smaller one, and then high doping is used to achieve ohmic contact, but this process is very complicated.

Summary

Countries such as Europe and the United States are continuing to increase their R&D support in the field of third-generation semiconductors. The third-generation semiconductor materials, led by GaN and SiC, are widely used and are a breakthrough in a new round of reforms in semiconductor, downstream power electronics, and communications industries.

In recent years, the domestic third-generation semiconductor industry has developed steadily, but there is still a certain gap with foreign advanced levels in terms of material indicators and device performance. The localization and high-end needs of the third-generation semiconductor industry are still urgent.