Silicon, Silicon Carbide and Gallium Nitride

Behind the common used digital products and high-tech electric vehicles, 5G base station, there are 3 core semiconductor materials: Silicon, Silicon Carbide and Gallium Nitride driving the industry. They are not alternative for each other, they are the experts in a team, and have the irreplaceable effort on different battlefields. Understanding their division of labor, we can see the development tree of the modern electronics industry.

1.Silicon: The base stone of the integrated circuits

Silicon is the undoubtedly king of the semiconductor, rule the all field of highly integrated, and complex computing. The computer CPU, mobile SoC, graphics processors, memory, flash memory, and various microcontrollers and digital logic chips, almost all are built on Silicon base.

Why Silicon dominate this field

1)Excellent integrated degree

Silicon has the great material properties, it can be grown a perfect SiO2 insulating film on the surface through the thermal oxidation process. This property is the base to build CMOS transistor, integrating billions even ten billions transistors on a small piece of chip, to achieve the extreme complex logistic functions.

2)Mature process and low cost

Through more than half century development, the process of Silicon is the result of the whole human industrial civilization. From purification, crystal pulling, to photolithography, etching, it has been forming a mature and huge industry chains, to produce the high-quality crystal with astonishing scale and extremely low cost.

3)Good balance

Silicon achieves the best balance between conductivity, switching speed, manufacturing cost, and thermal performance. While it may not match the performance of its upstart material in extreme performance, it is perfectly adequate and the most economical choice for handling complex digital signals and logic operations.

2.Silicon Carbide: Power Guardians on the High-volt Battlefield

SiC is the revolution material in the high-volt, high-power field. It is mainly used in "power devices" for power conversion and control. Such as main drive inverter, on-board charger, DC-DC converter in new energy vehicles; smart grid converter stations, industrial motor drives, and rail transit in industry and power grid; photovoltaic inverters and wind power converters in new energy power generation industry.

Why SiC suitable for high-voltage applications

1)Extremely high breakdown electric field strength

The breakdown electric field strength of SiC is 10 times higher then that of Silicon. It means fabricating the same voltage withstand device, the epitaxial layer of SiC can be thinner, the doping concentration can be higher, to reduce the on-resistance of the device. When the resistance becomes lower, the energy loss and heat generation can be significantly reduced when conduction.

2)Good thermal conductivity

Thermal conductivity of SiC is 3 times that of Silicon. In the high power application, the heating is the “top killer”. SiC device can more rapidly outlet the heating itself, to allow the system’s stable work under higher power density, or simplify the heat dissipation system.

3)High temperature working capacity

The working temperature of Silicon device typically is below 175°C, while SiC device can stable work at above 200°C. This makes it more reliable in high-temperature and harsh environments, such as electronic systems located close to the car engine.

3.Gallium Nitride: the speed pioneer on the high-frequency track

The core advantage of GaN is at high-frequency. It shines in two fields:

High-frequency power electronics (fast charging): the most widespread application currently, enabling us to use compact and highly efficient GaN fast chargers.

RF front-end: Power amplifiers in 5G communication base stations and radar systems in the defense industry.

Why GaN is the king of high-frequency performance

1)Extremely high electron saturation drift velocity: Electrons move extremely fast in GaN materials, meaning that transistors can achieve extremely high switching speeds. For switching power supplies, higher switching frequencies allow for the use of smaller and lighter capacitors and inductors, thus enabling charger miniaturization.

2)High electron mobility transistor (HEMT): As detailed in the previous article, the GaN-AlGaN heterojunction interface can automatically form a two-dimensional electron gas (2DEG), with extremely high electron concentration and mobility, resulting in extremely low on-resistance. This gives GaN devices the dual advantages of low conduction loss and low switching loss during high-speed switching.

3)Wider bandgap: Similar to silicon carbide, GaN also has a wide bandgap, making it resistant to high temperatures and high voltages, and more robust than silicon.