The combination of silicon and carbon endows this material with outstanding mechanical, chemical, and thermal properties, including:

(1) High thermal conductivity

(2) Low thermal expansion and excellent thermal shock resistance

(3) Low power consumption and switching losses

(4) High energy efficiency.

(5) High operating frequency and temperature (with a junction temperature of up to 200°C)

(7) Glass-passivated chips are small in size (at the same breakdown voltage).

(8) Intrinsic-body diode (MOSFET device)

(9) Excellent thermal management, which can reduce cooling requirements.

(10) Long service life

Silicon carbide is an ideal semiconductor for power‑electronics applications, primarily due to its ability to withstand high voltages—up to ten times higher than those tolerated by silicon. SiC‑based devices exhibit superior thermal conductivity, higher electron mobility, and lower power losses. SiC diodes and transistors can also operate at higher frequencies and temperatures without compromising reliability. Key applications of SiC devices, such as Schottky diodes and FET/MOSFET transistors, include converters, inverters, power supplies, battery chargers, and motor‑drive systems.

Although silicon is the most widely used semiconductor in electronic devices, it is beginning to reveal certain limitations, particularly in high-power applications. A key factor in these applications is the semiconductor’s bandgap, or energy gap. When the bandgap is large, the resulting electronic devices can be smaller, operate faster, and offer greater reliability. They can also function at higher temperatures, voltages, and frequencies than other semiconductors. While silicon has a bandgap of approximately 1.12 eV, silicon carbide boasts a bandgap nearly three times as large, at about 3.26 eV.

Power devices, particularly MOSFETs, must be capable of handling extremely high voltages. Because silicon carbide (SiC) exhibits a dielectric breakdown strength roughly ten times that of silicon, it can sustain very high breakdown voltages, ranging from 600 V to several kilovolts. SiC allows for doping concentrations higher than those achievable in silicon, and its drift region can be engineered to be exceptionally thin. A thinner drift region results in lower resistivity. Theoretically, at high voltages, the specific resistance of the drift region can be reduced to as low as one three-hundredth of that of silicon.

In high-power applications, IGBTs and bipolar transistors were traditionally favored to reduce on-state resistance at high breakdown voltages. However, these devices exhibit substantial switching losses, leading to thermal challenges that limit their use at high frequencies. By employing SiC, devices such as Schottky barrier diodes and MOSFETs can be fabricated to achieve high voltage ratings, low on-state resistance, and fast switching performance.

In its pure form, silicon carbide behaves like an electrical insulator. By controlling the addition of impurities or dopants, SiC can function as a semiconductor. P‑type semiconductors can be obtained through doping with aluminum, boron, or gallium, while nitrogen and phosphorus dopants yield N‑type semiconductors. Under certain conditions, silicon carbide exhibits conductivity, whereas under others it does not, depending on factors such as the voltage or intensity of infrared, visible, and ultraviolet radiation. Unlike other materials, silicon carbide allows for precise control over the P‑type and N‑type regions required in device fabrication across a broad range. For these reasons, SiC is a material well suited for power devices, capable of overcoming the limitations inherent to silicon.

Another important parameter is thermal conductivity, which indicates how effectively a semiconductor can dissipate the heat it generates. If a semiconductor cannot efficiently remove heat, it will impose limits on the maximum operating voltage and temperature that the device can withstand. This is another area where silicon carbide outperforms silicon: silicon carbide has a thermal conductivity of 1490 W/m·K, whereas silicon offers only 150 W/m·K.

Like silicon MOSFETs, SiC MOSFETs also feature an intrinsic body diode. One of the primary limitations of the body diode is its undesirable reverse‑recovery behavior, which occurs when the diode turns off while conducting forward current. Consequently, the reverse‑recovery time (trr) becomes a critical parameter for characterizing MOSFET performance. For example, comparing the trr of a 1000‑V silicon‑based MOSFET with that of a SiC‑based MOSFET reveals that the SiC MOSFET’s body diode exhibits extremely fast switching: both trr and irr are very small—practically negligible—and the associated energy loss, Err, is significantly reduced.

Another critical parameter of SiC MOSFETs is the short‑circuit withstand time (SCWT). Because SiC MOSFETs occupy a very small chip area and feature high current densities, their ability to endure short circuits that could lead to thermal runaway is generally lower than that of silicon‑based devices. For example, for a 2.247 kV MOSFET in a TO‑1 package, with Vdd = 700 V and Vgs = 18 V, the SCWT is approximately 8–10 μs. As Vgs decreases, the saturation current diminishes, and the withstand time increases. Similarly, reducing Vdd lowers the generated heat, further extending the withstand time. Since the turn‑off time of a SiC MOSFET is extremely short, a high dI/dt at elevated Vgs can produce severe voltage spikes. Therefore, soft turn‑off should be employed to gradually reduce the gate voltage and prevent overvoltage peaks.

Many electronic devices incorporate both low-voltage and high-voltage circuits, which are interconnected to perform control and power‑supply functions. For example, a traction inverter typically comprises a low‑voltage primary side—covering power, communication, and control circuits—and a secondary side—comprising high‑voltage circuits, the motor, the power stage, and auxiliary circuits. The controller on the primary side often relies on feedback signals from the high‑voltage side; without an isolation barrier, it is susceptible to damage. An isolation barrier electrically isolates the primary side from the secondary side, establishing a separate ground reference and enabling so‑called galvanic isolation. This prevents unwanted AC or DC signals from coupling between the two sides, thereby protecting power‑supply components from damage.

That concludes our comprehensive overview of “10 Things to Know About Gallium Nitride.” We hope you found this article helpful.

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