In the vast world of semiconductor materials, gallium nitride (GaN) silicon wafers are gradually emerging with their unique advantages and becoming a key force in promoting the progress of modern science and technology. As the name suggests, gallium nitride silicon wafers are the product of combining gallium nitride materials with silicon-based substrates. This ingenious combination combines the excellent electrical properties of gallium nitride with the advantages of silicon materials such as low cost, large size and mature process, bringing new development opportunities to the semiconductor industry.
1. Characteristics of gallium nitride silicon wafers
(1) Excellent electrical properties
1. Wide bandgap: Gallium nitride itself has a wide bandgap of about 3.4 electron volts (eV). Compared with traditional silicon materials (about 1.12eV), this enables gallium nitride silicon wafers to withstand higher voltages and effectively reduce leakage current, thereby showing excellent performance in high-power applications. For example, in power electronic devices, devices made of gallium nitride silicon wafers can work stably at higher voltages, greatly improving energy conversion efficiency.
2. High electron mobility: In the two-dimensional electron gas (2DEG) system of GaN silicon wafers, the electron mobility can be as high as about 2000cm²/(V・s). High electron mobility means that electrons can move quickly in the material, significantly improving the switching speed of the device, reducing the on-resistance, and reducing energy loss. This feature has important application value in the fields of high-speed switching devices and radio frequency devices, and can achieve higher frequency signal processing and more efficient power conversion.
3. High breakdown electric field strength: The breakdown electric field strength of GaN silicon wafers is as high as about 3MV/cm, which is more than an order of magnitude higher than that of silicon materials. This enables devices based on GaN silicon wafers to operate reliably in high voltage environments, and to achieve smaller device size and lighter weight under the same voltage requirements. In application scenarios that require high voltage and high power, such as power transmission and electric vehicle charging facilities, the high breakdown electric field strength advantage of GaN silicon wafers is fully reflected.
(2) Good thermal properties
GaN silicon wafers have good thermal conductivity, about 130 - 290W/(m・K). Higher thermal conductivity helps to quickly dissipate the heat generated during the operation of the device, maintain the performance stability of the device in a high temperature environment, and reduce the risk of device failure due to overheating, thereby improving the reliability and service life of the device. In high-power density applications, such as power modules in data centers and RF amplifiers in 5G base stations, good thermal performance is essential to ensure the normal operation of the equipment.
(3) Compatibility with silicon process
As the cornerstone of the semiconductor industry, silicon has a mature and complete manufacturing process and a huge industrial ecosystem. GaN silicon wafers are compatible with existing silicon processes, which greatly facilitates their large-scale production and wide application. By taking advantage of the advantages of silicon processes, GaN silicon wafers can achieve efficient and low-cost manufacturing without large-scale equipment updates and process changes, lowering the industry entry threshold and accelerating its commercialization process.
2. Preparation methods of GaN silicon wafers
(1) Metal organic chemical vapor deposition (MOCVD)
MOCVD is one of the common methods for preparing GaN silicon wafers. In this process, metal organic compounds (such as trimethylgallium (TMGa)) and ammonia (NH₃) are used as source materials to grow GaN thin films on the surface of silicon substrates by chemical vapor deposition in a reaction chamber at high temperature (usually 1000-1200℃) and low pressure (10-1000 Torr). MOCVD can accurately control various parameters in the growth process, such as temperature, gas flow, pressure, etc., to achieve high-quality and high-precision growth of GaN thin films. By optimizing the MOCVD process, the lattice mismatch and thermal mismatch problems between GaN thin films and silicon substrates can be effectively reduced, and the quality of GaN silicon wafers can be improved. GaN silicon wafers grown by this method have good crystal quality and uniformity, and are suitable for large-scale industrial production.
(2) Molecular Beam Epitaxy (MBE)
MBE is a technology for thin film growth in an ultra-high vacuum environment. In the MBE system, high-purity gallium atom beams and nitrogen atom beams (usually produced by cracking ammonia) are precisely controlled and directed to the surface of a heated silicon substrate. The atoms adsorb, migrate and combine with each other on the substrate surface, gradually forming a gallium nitride film. The growth process of MBE has the ability to precisely control the atomic level, can grow extremely thin and high-quality gallium nitride epitaxial layers, and can achieve precise control of material structure and doping. Although MBE equipment is expensive and has a slow growth rate, it has unique advantages in the preparation of high-quality gallium nitride quantum wells, quantum wires and other nanostructured materials, and is of great significance for the preparation of high-performance, high-value-added gallium nitride silicon wafer products. In some application fields that have extremely high quality requirements for gallium nitride silicon wafers, such as high-end RF devices and optoelectronic devices, gallium nitride silicon wafers prepared by MBE play an important role.
(3) Hydride Vapor Phase Epitaxy (HVPE)
HVPE uses hydrogen halide (such as HCl) to react with metal gallium to generate gaseous gallium halide (such as GaCl), which then reacts with ammonia at high temperature to deposit gallium nitride on a silicon substrate. This method has a fast growth rate and can obtain thicker gallium nitride films in a short time, which is suitable for preparing substrate materials for gallium nitride silicon wafers. However, the crystal quality of gallium nitride films grown by HVPE is slightly inferior to that of films grown by MOCVD and MBE, and usually requires subsequent processing and optimization to improve its performance. For example, by annealing the gallium nitride film grown by HVPE, its crystal structure can be improved and the defect density can be reduced, thereby improving the quality of gallium nitride silicon wafers. HVPE has a cost advantage in the large-scale production of gallium nitride silicon wafers. For some application fields that have relatively low performance requirements for gallium nitride silicon wafers but are more sensitive to cost, such as gallium nitride LED chip substrates for general lighting, gallium nitride silicon wafers prepared by HVPE have certain market competitiveness.
3. Application fields of GaN silicon wafers
(1) Power management field
1. High-efficiency chargers: With the growing demand for fast charging of electronic devices, GaN silicon wafers have been widely used in the field of chargers. Due to the characteristics of high switching speed and low on-resistance of GaN silicon wafer devices, chargers can operate at higher frequencies, which significantly reduces the size and weight of magnetic components such as transformers and inductors, and realizes the miniaturization and efficiency of chargers. Compared with traditional silicon-based chargers, GaN silicon wafer chargers can fully charge devices in a shorter time, while having higher charging efficiency, reducing energy loss and heating problems. For example, many 65W, 100W or even higher power fast charging chargers using GaN silicon wafer technology have appeared on the market, bringing consumers a convenient and efficient charging experience.
2. Server power supply: In data centers, servers require a large amount of power supply, and the efficiency and volume of power supply become key factors. GaN silicon wafer power devices can improve the conversion efficiency of server power supply, reduce energy consumption, and reduce heat dissipation costs. Server power supplies using GaN silicon wafer technology can achieve a more compact design while maintaining high power output, saving space for data centers and reducing operating costs. According to statistics, the conversion efficiency of server power supplies using GaN silicon wafer power devices can be increased by 2% - 5% compared to traditional silicon-based power supplies. In large-scale data center applications, this will bring significant energy savings and economic benefits.
3. Automotive power supply: In electric vehicles and hybrid vehicles, GaN silicon wafers can be used in power systems such as on-board chargers and DC-DC converters. The high performance of GaN silicon wafer devices can improve the efficiency of automotive power systems, extend battery life, and reduce the size and weight of power modules, which is conducive to the lightweight design of automobiles and improves the overall performance of automobiles. For example, in the on-board charger of electric vehicles, the use of GaN silicon wafer technology can shorten the charging time, improve the charging efficiency, and meet the user's demand for fast charging; in DC-DC converters, GaN silicon wafer devices can achieve higher power density, reduce the size of power modules, and provide more possibilities for the rational use of the interior space of the car.
(2) Radio Frequency (RF) Field
1. 5G communication base station: 5G communication technology has put forward higher requirements for RF devices, which need to have the characteristics of high power, high efficiency, high frequency and miniaturization. GaN silicon wafer RF devices have become an ideal choice for 5G base station construction due to their excellent performance. GaN silicon wafer power amplifiers can provide greater output power at higher frequencies, improving the signal coverage and communication quality of base stations. Compared with traditional gallium arsenide (GaAs) RF devices, GaN silicon wafer devices have higher power density and efficiency, which can effectively reduce the energy consumption and operating costs of base stations. It is estimated that the use of GaN silicon wafer power amplifiers in 5G base stations can reduce the energy consumption of base stations by 30% - 50%, while improving the stability and reliability of signal transmission.
2. Satellite communication: In satellite communication systems, due to the limited energy of satellites, the efficiency and power requirements of RF devices are extremely high. GaN silicon wafer RF devices can work stably in the harsh environment of satellites, and with their high power and high efficiency characteristics, they ensure reliable communication connections between satellites and ground stations. At the same time, the miniaturization advantage of GaN silicon wafer devices helps to reduce the weight of satellites and reduce launch costs. For example, in low-orbit satellite communication systems, the use of GaN silicon wafer RF devices can improve the communication capacity and coverage of satellites and meet the growing demand for satellite communications.
3. Radar system: GaN silicon wafers also have broad application prospects in the radar field. High-power GaN silicon wafer RF devices can improve the detection distance, resolution and anti-interference ability of radars. For example, in military radars, GaN silicon wafer radars can detect targets more accurately and improve combat effectiveness; in civilian radars, such as air traffic control radars and weather radars, the application of GaN silicon wafer technology can improve the performance and reliability of radar systems and ensure the accuracy of aviation safety and meteorological monitoring.
(3) Lighting field
1. High-brightness light-emitting diodes (LEDs): GaN silicon wafers are one of the core materials for manufacturing high-brightness LEDs. By growing epitaxial layers of different structures on GaN silicon wafers and doping them with appropriate impurities, the color of the light emitted by the LED can be adjusted to achieve light emission from blue light to white light and other colors. GaN silicon wafer-based LEDs have the advantages of high luminous efficiency, long life, and low energy consumption. They are widely used in lighting fields such as indoor lighting, outdoor lighting, automotive lighting, and display backlights. In indoor lighting, GaN silicon wafer-based LEDs can provide high-quality lighting that is closer to natural light while saving a lot of energy; in automotive lighting, their high brightness and fast response characteristics improve driving safety.
2. Ultraviolet light-emitting diodes (UV-LEDs): GaN silicon wafers can also be used to manufacture UV-light-emitting diodes. UV-LEDs have important applications in sterilization, curing, medical treatment, anti-counterfeiting and other fields. For example, in the fields of water purification and air purification, UV-LEDs can effectively kill bacteria and viruses; in the printing and coatings industry, UV-LEDs are used to cure inks and coatings to improve production efficiency and product quality; in the medical field, UV-LEDs can be used for phototherapy and skin treatment. GaN silicon wafer-based UV-LEDs have the advantages of high luminous efficiency and precise control of wavelength, which can meet the needs of different application scenarios.
(4) Other fields
1. Motor drive: In industrial motor drive and electric vehicle motor drive systems, GaN silicon power devices can improve the efficiency and power density of motors. Due to the high switching speed of GaN silicon devices, more precise motor control can be achieved, the torque pulsation of the motor can be reduced, the energy consumption and heat generation of the motor can be reduced, and the service life of the motor can be extended. For example, in industrial automation production lines, motor drive systems using GaN silicon power devices can improve the operating efficiency and stability of production equipment; in electric vehicles, GaN silicon motor drive systems can improve the acceleration performance and driving range of vehicles.
2. Consumer electronics: In addition to chargers, GaN silicon wafers are gradually being used in other consumer electronic products, such as power management modules for computer motherboards and power systems for game consoles. In these applications, the high performance of GaN silicon wafers helps to improve the performance and stability of products, while achieving miniaturization and thinness of products, meeting consumers' demand for portability and high performance of electronic products. For example, some high-end computer motherboards use gallium nitride silicon wafer power management chips, which can provide more stable and efficient power supply for core components such as CPU and GPU, and improve the overall performance of the computer.
4. The development status and challenges of gallium nitride silicon wafers
(1) Development status
At present, gallium nitride silicon wafer technology has made significant progress and has been commercialized in many fields. Globally, many semiconductor companies and research institutions have increased their investment in the research and development of gallium nitride silicon wafer technology, which has promoted the rapid development of the gallium nitride silicon wafer industry. In the field of power electronics, the market share of gallium nitride silicon wafer power devices has gradually increased, and more and more electronic products have begun to use gallium nitride silicon wafer chargers, power modules, etc.; in the field of radio frequency, gallium nitride silicon wafer radio frequency devices are also increasingly widely used in 5G communication base stations, satellite communications and other fields. At the same time, with the continuous advancement of technology, the size of gallium nitride silicon wafers has continued to increase, the quality has continued to improve, and the cost has gradually decreased, laying the foundation for its wider application.
(2) Challenges
1. Lattice mismatch and thermal mismatch: There is a large lattice mismatch and thermal mismatch between GaN and silicon substrate, which will cause a large number of dislocations and defects during the growth process, affecting the crystal quality and performance of GaN silicon wafers. In order to solve this problem, it is necessary to further optimize the growth process and develop new buffer layer structures and materials to reduce the negative impact of lattice mismatch and thermal mismatch. For example, the use of multi-layer buffer layers, strain engineering and other technical means can effectively improve the crystal quality of GaN silicon wafers, but these methods often increase the complexity and cost of the process.
2. Cost issue: Although GaN silicon wafer technology is constantly developing, its cost is still relatively high, which limits its large-scale application. The main reasons for the high cost include complex preparation process, expensive equipment, and the need to improve the yield rate. In order to reduce costs, on the one hand, it is necessary to continuously optimize the preparation process, improve production efficiency, and reduce equipment costs; on the other hand, it is necessary to expand the scale of the industry, achieve scale effects, and reduce raw material procurement costs and production costs. In addition, improving the yield rate of GaN silicon wafers is also one of the key factors in reducing costs, and it is necessary to strengthen the quality control of the production process and the research and development of detection technology.
3. Reliability issues: In practical applications, the reliability of GaN silicon wafer devices needs to be further verified and improved. Since GaN silicon wafer devices work under extreme conditions such as high voltage, high frequency and high temperature, they may face problems such as device degradation and failure. It is necessary to conduct in-depth research on the failure mechanism of GaN silicon wafer devices, and improve the device structure design, optimize the packaging process and strengthen the reliability test.
