Nowadays, we are standing at the starting point of the fourth industrial revolution, where new technologies such as artificial intelligence, 5G technology, new energy, and new materials have become the darling of the times. And all of this cannot be separated from the development of the semiconductor industry. In the semiconductor industry, there is a material that has become the key to today's semiconductor development, and it is silicon carbide (SiC), which is the only composite of silicon and carbon, commonly known as diamond. SiC exists in nature in the form of mineral carbosilicate, but it is very rare.
Silicon carbide materials are listed as the third-generation semiconductor materials in the industry due to their excellent performance, with a breakdown field strength 10 times that of silicon and a thermal conductivity 2.5 times that of silicon. MOS devices made of silicon carbide materials can operate in high temperature environments above 200 degrees Celsius, with extremely low switching losses and high-frequency operating capabilities, reducing module size and weight, significantly improving system efficiency, and promoting energy conservation and consumption reduction. They are widely used in high-tech fields such as wind and solar power generation, photovoltaic inverters, UPS energy storage, new energy vehicles, aerospace and military industry, especially in the following areas:
1. LED
The phenomenon of electroluminescence was first discovered in 1907 using silicon carbide light-emitting diodes (LEDs). Soon, the first batch of commercial SiC based LEDs were produced. In the 1970s, the former Soviet Union produced yellow SiC LEDs, and in the 1980s, blue LEDs were widely produced worldwide. Later, gallium nitride (GaN) LEDs were introduced, which emitted light tens or even hundreds of times brighter than SiC LEDs, and SiC LEDs were almost discontinued as a result. However, SiC is still commonly used as a substrate for GaN devices and is also used as a high-power LED heat sink.
2. Lightning arrester
Before reaching the threshold voltage (VT), SiC has a high resistance. After reaching the threshold voltage, its resistance will significantly decrease until the applied voltage drops below VT. The earliest SiC electrical application to utilize this feature was the lightning arrester in distribution systems (as shown in the figure).
Due to the presence of varistors, SiC core blocks can be connected between high-voltage wires and the ground. If the power line is struck by lightning, the line voltage will rise and exceed the threshold voltage (VT) of the SiC lightning arrester, directing the lightning current to the ground (rather than the power line), thus not causing any harm. However, these SiC lightning arresters are too conductive under normal operating voltage of power lines. Therefore, a spark gap must be connected in series. When lightning strikes increase the voltage of the power line conductor, the spark gap will ionize and conduct electricity, effectively connecting the SiC lightning arrester between the power line and the ground. Later, relevant personnel discovered that the spark gap used in the lightning arrester was not reliable. Due to material failure, dust or salt intrusion, there may be situations where the spark gap cannot trigger the arc when needed, or the arc cannot suddenly extinguish after lightning strikes. SiC lightning arresters were originally designed to eliminate dependence on spark gaps, but due to their unreliability, gap free SiC lightning arresters are mostly replaced by gap free varistors using zinc oxide core blocks.
3. SiC in Power Electronics
Designers of power electronic systems are using SiC for innovation and fully utilizing SiC devices. SiC is rapidly being used in many exciting applications to address the energy and cost challenges of developing efficient, high-power devices, which will help drive the 21st century. One area where SiC has been found to be particularly advantageous for innovation is electric vehicles - think of any vehicle that is completely or partially powered by electricity, such as electric bicycles and electric vehicles (EVs). Electric vehicles use new components and frequency converters to power the engine, onboard battery chargers and induction chargers, as well as inverters used to assist loads such as power steering. These systems require high-voltage batteries, which was one of the main obstacles to the early adoption of electric vehicles. However, using SiC can reduce the size of electric vehicle batteries while lowering the overall cost for consumers, thereby lowering the barriers to adoption. In addition, the thermal performance of SiC also enables car manufacturers to reduce the cost of cooling powertrain components. This brings more benefits by reducing the weight and cost of electric vehicles.