Comprehensive interpretation of compound semiconductor GaAs, GaN, SiC technology advantages and application areas
Time：2020.08.10
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Si is the most widely used semiconductor material, but it cannot break through bottlenecks such as high temperature, high power, and high frequency. The binary compound semiconductor material GaAs/GaN/SiC has the characteristics of high power density, low energy consumption, high temperature resistance, high luminous efficiency, etc., which can make up for the deficiencies of Si materials, and has significant advantages in applications such as radio frequency, power devices, optoelectronics, and defense industry. . This article comprehensively introduces the technical advantages of GaAs/GaN/SiC and its applications in 5G, new energy vehicles and other emerging fields.
1. Compound semiconductors have significant performance advantages and are expected to usher in rapid penetration
1.1 GaAs/GaN/SiC has significant advantages and different application areas
Commonly used semiconductor materials are divided into element semiconductors and compound semiconductors. Elemental semiconductors are semiconductor materials made from a single element. There are mainly silicon, germanium, selenium, etc., with silicon and germanium being the most widely used. Compound semiconductors are divided into binary systems, ternary systems, multi-component systems and organic compound semiconductors. Binary compound semiconductors include III-V groups (such as gallium arsenide, gallium phosphide, silicon carbide, etc.).
Silicon (Si) is an earlier and most widely used semiconductor material. The earliest semiconductor transistors used germanium (Ge)-based materials, but due to the small reserves of Ge and the difficulty of purification, they were gradually replaced by Si. Si has become the most widely used semiconductor material because of its abundant reserves, mature technology, and low cost. It is currently widely used in various discrete devices and integrated circuits, electronic information network engineering and other fields. For applications such as optics, binary compound semiconductor materials have more advantages.
The binary compound semiconductor material GaAs/GaN/SiC has the characteristics of high power density, low energy consumption, high temperature resistance, and high luminous efficiency. It has significant advantages in applications such as radio frequency, power devices, optoelectronics, and national defense and military industries.
GaAs is one of the more important and most mature compound semiconductor materials. Compared with Si, GaAs materials have the characteristics of large forbidden band width and high electron mobility, which can significantly reduce the radio frequency size, reduce power consumption, and also have cost advantages. Compared with emerging binary compound semiconductor materials such as GaN and SiC, GaAs technology is mature and has obvious cost advantages. GaAs is widely used in radio frequency and optoelectronic fields.
As a wide bandgap semiconductor, GaN is mainly used in microwave radio frequency, power electronics, optoelectronics and other fields because of its high power density, low energy consumption, suitable for high frequencies, and support for wider bandwidth. The microwave radio frequency direction is mainly 5G communication and satellite communication applications; power electronics includes consumer electronics fast charging, new energy vehicles and other applications; the optoelectronic direction is mainly LED and other fields. At present, GaN technology is still in the rapid development stage, and the cost is relatively high.
SiC has a higher carrier mobility, can provide a higher current density, and is resistant to high temperature and high voltage, so it is often used as a power device. SiC has advantages in high-power areas with voltages of 600V and above. Similar to GaN, SiC technology is also in the rapid development stage, and the cost is relatively high.
GaAs/GaN/SiC application areas are different. GaAs is currently the most widely used radio frequency material and is widely used in radio frequency, wireless communication and special applications. The operating frequency of GaAs applications is mainly within 8G Hz, which is suitable for low and medium power devices, such as micro base stations and mobile phone radio frequency materials. In the high-power radio frequency direction, GaN has obvious advantages and is a necessary material for 5G macro base stations. In addition, as a fast charging material, GaN can significantly reduce the size of the charger and reduce power consumption. It is currently rapidly penetrating in the fast charging of mobile phones. SiC is an ideal material for power devices, especially in terms of high voltage resistance (>600V). It has significant performance advantages and is widely used in new energy vehicles, power equipment and other fields.
The price of SiC/GaN devices continues to decline. Overall, the current cost of SiC/GaN devices is still much higher than that of Si products. However, as technology advances, product yields increase, and economies of scale increase, the prices of SiC/GaN devices continue to decline. In terms of power products, taking 650V SiC MOSFET as an example, the price of its products has dropped from RMB 3.44/A in mid-2018 to RMB 2.24/A at the end of 2019. In terms of radio frequency products, the recent price cuts of RF GaN HEMT are even more significant. The average price at the end of 2019 has dropped by nearly 23% compared with 2018.
Benefiting from the maturity of SiC/GaN device technology and cost reduction, SiC/GaN devices are expected to accelerate penetration. Thanks to the improvement of the performance of SiC/GaN power products, it is expected to be widely used in new energy vehicles, fast charging and other markets. According to Yole’s forecast, the market size of SiC and GaN power electronic devices will grow to 1.4 billion and 1.4 billion in 2023. 370 million US dollars, the market penetration rate reached 3.75% and 1% respectively. GaN RF devices are under the strong demand for 5G macro base station construction and national defense construction, and the cost of superimposed GaN RF devices has fallen, and demand is expected to increase rapidly. According to Yole data forecasts, the demand for GaN RF devices will reach 194.3 million in 2023, 19-23 The annual CAGR reached 85.8%.
Benefiting from the strong demand for RF and optoelectronics, GaAs is expected to maintain sustained high growth. On the radio frequency side, 5G mobile phones require more PA, and demand for GaAs is expected to maintain steady growth; demand for GaAs for mobile phone WIFI PA and router WIFI PA is expected to maintain rapid growth. Optoelectronics, benefiting from the rapid penetration of 3D depth cameras in mobile phones, GaAs lasers are expected to maintain rapid growth. According to the report of China Industry Information Network, the global GaAs output value is expected to increase from USD 8.9 billion in 2018 to USD 14.3 billion in 2023, with a CAGR of 10% in 19-23.
2.1 GaAs PA is the mainstream technology, benefiting from industry trends such as 5G
The penetration rate of 5G mobile phones has increased rapidly. The mobile phone market is ushering in a wave of 5G replacement. The global sales of 5G mobile phones in 2019 were 18.7 million units, with a penetration rate of approximately 1.4%. GSMA predicts that 5G mobile phone shipments in 2025 are expected to reach 700 million units, with a penetration rate of 47%. With the deployment of domestic 5G networks exceeding expectations, 5G users in China have rapidly increased. As of the end of March 20, China Mobile had more than 30 million 5G users. It is conservatively estimated that the three major operators have more than 60 million 5G users. .
5G mobile phones need more power amplifiers. 4G radio frequency communication needs to use 5-mode 13-frequency, and an average of 7 PAs are used. As 5G has new frequency bands (n41 2.6GHz, n77 3.5GHz and n79 4.8GHz), high frequency bands above 6GHz will need to be added in the future. At the same time, it will continue to be compatible with 4G, 3G, and 2G standards. Therefore, 5G mobile phones need more PAs. It can be up to 16 and is expected to exceed 10 on average.
The penetration rate of GaAs in mobile phone PA is expected to continue to increase. The performance of Si CMOS PA in terms of output power and operating frequency is obviously insufficient, and it is difficult to adapt to the high frequency and high power of the 5G era. However, the current GaN PA technology is still not mature enough and the cost is relatively high. GaAs PA has excellent performance and can meet the needs of 5G mobile phones in the sub-6 G Hz frequency band, and the penetration rate is expected to continue to increase.
Benefiting from the high volume of mobile phone PAs, the demand for GaAs for radio frequency is expected to continue to grow. According to Yole's forecast, the demand for GaAs for mobile phone PAs will increase from 439,000 pieces/year (equivalent to 6-inch pieces) in 19 years to 542,000 pieces/year in 25 years. In addition, the number of gallium arsenide wafers consumed by mobile phone WIFI PA and router WIFI PA has also shown rapid growth, which is expected to increase from 106,000 wafers/year in 19 to 180,000 wafers/year in 25 years. Benefiting from the steady growth in demand for mobile phone PA, the rapid growth of mobile phone WIFI PA and router WIFI PA, the demand for gallium arsenide for radio frequency is expected to maintain steady growth. The demand for 6-inch gallium arsenide wafers for the entire GaAs RF will increase from 744,000 in 19 /Year growth to 941,000 pieces/year in 25 years, CAGR is about 4%.
2.2 3D depth cameras are fully commercialized, and GaAs optoelectronics has a promising future
GaAs has a direct transition type energy band structure, and the optical transition between the bottom of the conduction band and the top of the valence band can proceed vertically, and the luminous efficiency is high. GaAs materials are mainly used in the production of red light and infrared devices
3D depth cameras are fully launched for commercial use. In 2017, Apple launched the iPhone X with an integrated face recognition structured light front camera, and started the commercial use of 3D depth cameras on mobile phones. The structured light emitting source uses a GaAs laser (vertical cavity surface laser, VCSEL). In March 2020, Apple launched the iPad Pro with a rear ToF camera, using a similar VCSEL emission light source. Apple is also expected to adopt a rear ToF camera on the iPhone released in September 2020, forming a front structured light + rear ToF With the dual 3D depth camera configuration, the VCSEL usage of a single mobile phone is expected to reach 2. Huawei, OPPO, ViVO, Xiaomi, Samsung and other mobile phone manufacturers are also expected to gradually deploy ToF cameras on their phones and use VCSEL light sources. According to Yole's report, the shipment of 3D cameras in 2018 was approximately 73 million, and it is expected to grow to 890 million by 2023, with a CAGR of 65%.
3. GaN: 5G key device with significant advantages in the RF/power electronics field
3.1 GaN: suitable for high frequency, high power and low voltage applications
GaN devices began to be used in light-emitting diodes in 1990, opening the door to their commercialization. As a wide bandgap semiconductor, it has the characteristics of large forbidden band width, high breakdown field strength, high saturated electron migration rate, high thermal conductivity, low dielectric constant, and strong radiation resistance. It is suitable for making high frequency and large Power, high-density integration and radiation-resistant electronic devices are widely used in power electronics fields such as smart grids, high-speed rail transit, and microwave radio frequency fields such as 5G base stations and radars. According to data from Jinzhi Innovation, in 2017, LED, microwave radio frequency, and power electronics (power devices) applications accounted for 70%, 17% and 11% of the domestic GaN downstream.
In the field of electronic devices, GaN is more suitable for high-frequency, high-power, and low-voltage applications. In terms of radio frequency applications, compared to GaAs and Si, GaN has a higher electron saturation drift speed, a larger band gap, and lower conduction loss, making it suitable for high-power, high-frequency radio frequency applications. In terms of power semiconductor applications, it is mainly used in the low-voltage field because it is not as good as SiC in high-voltage scenarios. Specifically, the current advantage of GaN is in the low voltage field of 200-600V, while SiC is mainly used in the medium and high voltage field of 600V or more.
Strong demand for RF power amplifiers
There are currently three main processes for RF power amplifiers: GaAs, GaN and Si-based LDMOS. The aforementioned GaAs output power is low (generally less than 50W), and is mainly used in the construction of terminal radio frequency front-ends and micro-cell base stations. However, GaN and LDMOS have higher output power and are mainly used in radio frequency units of macro base stations. In the construction of 4G base stations, LDMOS devices are the mainstream of the market. It is expected that in the construction of 5G, GaN devices will gradually become the mainstream of macro base station applications. In addition, the military GaN RF market will also maintain a high boom. It is expected that the proportion of GaN in RF power device applications will continue to increase significantly.
5G macro base stations put forward higher requirements for radio frequency devices. The main challenges that 5G brings to the construction of base stations are: 1) Higher frequency and larger bandwidth: 4G's frequency range is 1.88GHz-2.635GHz, while 5G's Sub-6GHz frequency band and millimeter wave frequency band can reach 0.45GHz respectively -6GHz and 24.25GHz-52.6GHz, the component carrier bandwidth can reach 100MHz. 2) The demand for higher power efficiency; 3) The demand for higher power density: According to Huawei, the power of 5G base stations will exceed 11Kw, which is 68% higher than that of 4G base stations. Operators need to greatly increase the power density to achieve the same size Provide higher power in the space. 4) Smaller size: 5G Massive MIMO and beamforming technology use array antennas, the number of components has increased significantly, and the demand for equipment miniaturization drives the miniaturization of internal components.
GaN radio frequency devices are more suitable for 5G macro base stations. GaN radio frequency devices can well meet the high requirements of 5G macro base stations: 1) Traditional LDMOS only performs well at 3.5GHz and below, and cannot adapt to the high frequency of 5G, while the frequency range that GaN adapts has expanded to 40Hz or even higher. The demand for 5G high frequency. In addition, the higher efficiency, higher output impedance and lower parasitic capacitance of GaN devices can make it easier to achieve bandwidth matching. 2) GaN has soft compression characteristics, easier predistortion and linearization, and higher efficiency. 3) GaN can achieve higher power density, reaching about 4 times the power density of LDMOS devices. 4) In terms of volume, GaN package size is only 1/4-1/7 of LDMOS.
Benefiting from the rapid increase in 5G macro base stations, the consumption of GaN devices is expected to increase rapidly. Major countries in the world such as the United States, Japan, China, South Korea and other countries have already started 5G commercial use, and base station construction is in a phase of gradual increase in volume. 5G macro base stations will be based on 64-channel large-scale array antennas. Based on three sectors, the demand for PAs for a single base station will be as high as 192. According to the forecast of Tuo Dai Industry Research Institute, the construction of domestic 5G macro base stations will reach a peak around 2023, with an annual increase of more than 1.15 million and corresponding PA demand as high as 221 million. With the decline in the cost of GaN devices and the maturity of the process, the penetration rate of GaN PA will continue to increase. The Top Industry Research Institute estimates that the proportion of GaN in the 5G macro base station PA in 2019 will be about 50%, and it is expected that the proportion of GaN will reach 80%, corresponding to the domestic market demand of 11.26 billion yuan.
Military radar upgrades drive the rapid volume of the GaN RF market. Military radar upgrades are embodied in two aspects: First, the GaN-based active electronically scanned array (AESA) radar system replaces the original GaAs-based AESA radar system and the traveling wave tube (TWT)-based system. This is mainly due to two reasons: on the one hand, the high power of GaN improves the anti-interference ability and expands the range or search range; on the other hand, after the use of GaN, a smaller aperture can be formed compared to those without GaN. The larger aperture has the same range and search range. Therefore, upgrading to GaN-based AESA radar systems has become a trend, and the military of various countries is upgrading to AESA radar and GaN chips at the same time. The second is the upgrade of the AESA antenna architecture. The next generation of AESA antennas will combine in the same RF front-end to produce different working modes, including radar, communications and electronic warfare. This will generate higher demand for monolithic microwave integrated circuits (MMIC), corresponding to The demand for GaN will increase accordingly. Driven by the above two factors, the military radio frequency market continues to boom.
The explosion of 5G macro base stations and military applications is expected to promote the rapid growth of the GaN RF market. According to Qorvo’s forecast, the global base station and military GaN RF device markets will grow from USD 210 million and USD 200 million in 2018 to USD 1.36 billion and USD 520 million in 2022, with CAGR of 60% and 27%, respectively. The device market will reach USD 1.91 billion in 2022 from USD 430 million in 2018, with a CAGR of approximately 45%.
Quick charge and quick volume
The technical advantages of GaN power devices are obvious: GaN power devices have high switching frequency, small on-resistance, small capacitance, large band gap, high temperature resistance, high energy density, high power density, and can maintain a high efficiency level under high frequency conditions. More efficient fast charging, suitable for high-power electronic products. In comparison, the faster the switching speed of traditional silicon devices, the lower the efficiency, and there are technical obstacles in achieving high-power charging.
GaN can integrate peripheral drivers and reduce the overall volume: traditional silicon devices have a vertical structure and cannot integrate peripheral drivers; GaN power devices have a planar architecture that can integrate peripheral driver and control circuits, making the IC smaller and significantly reducing costs.
Many GaN chargers have come out, and the product trend is obvious. OPPO became the world's first mobile phone manufacturer to launch a GaN charger in November last year, but its 65W fast charge only supports its own SuperVOOC fast charge protocol, and the interface is USB-A, which is not compatible with most laptops and is only suitable for OPPO product. At present, many charger manufacturers have launched GaN charging products. At this year's CES2020, 30 manufacturers exhibited 66 GaN fast charging chargers, all of which are smaller in size than traditional chargers, and most of the products support fast charging protocols such as PD and QC, and are equipped with USB-C interfaces. The upcoming Realme X50 Pro is expected to use 65W SuperDart super flash GaN charger. The increase in power consumption of 5G mobile phones has brought about a stronger demand for fast charging. Chargers with 65W and even above 100W are expected to become popular quickly, and GaN fast-charging chargers are expected to become the mainstream of the market.
The GaN power semiconductor market is growing rapidly. According to Yole, the global GaN power semiconductor market was only 8.73 million U.S. dollars in 2018. It is conservatively predicted that it will exceed 350 million U.S. dollars by 2024, and the average annual compound growth rate in 18-24 will reach 85%. According to optimistic estimates, mobile phone manufacturers such as Apple, Samsung, and Huawei also use GaN power adapters. It is estimated that the global GaN power semiconductor market will exceed 750 million US dollars in 2024. We speculate that if notebook computers, tablet computers, light hybrid electric vehicles, etc. all adopt GaN fast charging, the market space is expected to be greater.
4. SiC: a key device for high-voltage power semiconductors, benefiting from the rapid growth of new energy vehicles
4.1 SiC: Mainly used in the field of high-voltage power semiconductors
SiC is a new type of semiconductor material. The research and development of SiC power devices has started since the 1970s. In 2001, Infineon launched the first SiC device-300V~600V (16A) SiC Schottky diode. Subsequently, SiC Power devices have begun rapid commercial development. In 2007, SiC JFET and BJT were launched. In 2011, the first 1.2kV SiC MOSFET was launched. In 2015, SiC Trench MOSFET began to be introduced into the market. In 2016 and 2017, 3.3kV and 6.4kV SiC power MOSFETs With the appearance of samples, SiC power devices continue to expand to higher voltages. In 2018, Tesla Model 3 used SiC power devices for the first time. With the development of electric vehicles, the SiC market has entered a new stage of rapid development.
SiC is more suitable for high-voltage power device applications and has a bright future. Compared with traditional Si semiconductors, SiC has a wide band gap (about 3 times that of Si), high breakdown field strength (over 9 times that of Si), high thermal conductivity (over 2.5 times that of Si), and high operating temperature (Si The performance characteristics of high electron mobility (more than 2 times of Si), low charge loss, high pressure resistance, high temperature and high frequency performance in applications, can reduce device power consumption, save heat dissipation costs, and small Chemical devices, and can be used for large-scale high-voltage equipment. In the future, it has the potential to replace Si-based devices in applications in multiple fields such as automobiles, industry, IT and consumer electronics, and the future has a bright future.
4.2 The number of new energy vehicles and charging piles is growing rapidly, and the demand for SiC devices is strong
In the next few years, new energy vehicles and charging piles will become the main driving force for the rapid growth of the SiC power semiconductor market. In new energy vehicle applications, SiC power semiconductors can achieve lighter weight and higher efficiency than Si-based devices. In the new energy vehicle system, the components using power semiconductors mainly include: DC/AC inverters, DC/DC converters, motor drivers and on-board chargers (OBC). At present, the power semiconductor devices in electric vehicles are mainly Si-based devices, but the emerging SiC power devices have more advantages in performance. In the design of DC/AC inverters, SiC modules instead of Si modules can significantly reduce the weight and size of the inverter, while saving energy. At similar power levels, the weight of the SiC module inverter can be reduced 6kg, the size can be reduced by 43%, while the switching loss is reduced by 75%. In the design of DC/DC converters, SiC-MOSFET can replace Si-IGBT to increase input and output voltage, and can increase switching frequency (the higher the switching frequency, the smaller the output capacitance and inductance, thus saving circuit board area) and power Density, miniaturization of components. In addition, according to the data of Aachen University, under the same input power, the efficiency of the three-phase SiC DC/DC converter is about 1% higher than the efficiency of the corresponding single-phase Si DC/DC converter on average.
The light weight, high efficiency, and high temperature resistance of SiC power devices help effectively reduce the cost of new energy vehicle systems. Take the SiC power device that was first mounted in the Tesla Model 3 in 2018 as an example. Its lightweight features save the internal space of electric vehicles, and its high-efficiency features effectively reduce the cost of electric vehicle batteries. High temperature resistance (200 degrees can also be normal Work) characteristics reduce the requirements for the cooling system and save cooling costs. Although the application of SiC power devices has increased the initial cost by about US$300, the above improvements can save nearly US$2,000 in system costs. Overall, the use of SiC power devices has brought positive benefits of more than US$1700.
Benefiting from the substantial increase in the value of power semiconductors in new energy vehicles and the increase in sales of new energy vehicles, SiC power devices for vehicles are expected to fully benefit. According to Infineon’s statistics, the upgrade of traditional fuel vehicles to new energy vehicles has greatly increased the value of semiconductor devices from an average of US$355 to US$695. Among them, semiconductor power devices have increased significantly, from US$17 to 15 Times to 265 US dollars, which brings greater opportunities for power semiconductors, especially SiC power semiconductors. According to Infineon's forecast, the penetration rate of SiC devices in new energy vehicles is expected to continue to increase, from 3% in 2020 to 20% in 2025. According to the forecast of the International Energy Agency (IEA), in the context of sustainable development, the global number of electric vehicles will increase from 7.2 million in 2019 at an average annual growth rate of over 36% to 245 million in 2030. Under the influence of the above two factors, it is expected that automotive SiC power devices will maintain strong demand.
The acceleration of charging pile construction has opened up a new incremental market for the SiC power device market. According to data from the National Development and Reform Commission, as of the end of 2019, there were more than 1.2 million charging facilities in China, which is still a shortcoming compared with more than 3.8 million new energy vehicles. The future construction will continue to accelerate, and new charging facilities are expected in 2020 alone. There are more than 600,000 piles. A DC charging pile requires about 170 MOS. SiC devices used in charging piles have the advantages of high power density, ultra-small size, and support fast charging, which has become a future development trend. According to CASA calculations, the penetration rate of SiC power devices in charging piles in 2018 was only about 10%. In the future, the penetration rate of SiC in charging piles will increase and the construction of charging piles will accelerate. The charging pile market is expected to bring a significant market increase for SiC power devices. SiC is more suitable for high-voltage power device applications and has a bright future. Compared with traditional Si semiconductors, SiC has a wide band gap (about 3 times that of Si), high breakdown field strength (over 9 times that of Si), high thermal conductivity (over 2.5 times that of Si), and high operating temperature (Si The performance characteristics of high electron mobility (more than 2 times of Si), low charge loss, high pressure resistance, high temperature and high frequency performance in applications, can reduce device power consumption, save heat dissipation costs, and small Chemical devices, and can be used for large-scale high-voltage equipment. In the future, it has the potential to replace Si-based devices in applications in multiple fields such as automobiles, industry, IT and consumer electronics, and the future has a bright future.
