Crystals For Extreme Electronics

Like silicon, silicon carbide is semiconductor and in some aspects, its characteristics are even better. Electrical strength of silicon carbide is ten times higher than that of silicon, heat conductivity is three times higher. Crystals of silicon carbide are almost perfect for power electronics. They can work at high current density (more than 10 kA per square centimeter) and voltage up to 4.5 kV, unachievable for silicon. Moreover, charge-drift velocity is twice higher in silicon carbide providing better commutation characteristics.

“If silicon carbide instead of silicon is used in power diodes, up to 20% of energy will be saved”, said Professor Yury Tairov, head of Microelectronics Department in St-Petersburg Electrotechnical University.

The problem is how to make high-quality crystals of silicon carbide for a reasonable cost. Commonly a sublimation technique (so-called Lely Method) is used. In this technique a crystal grows from vaporized silicon carbide in a special chamber. Tairov and his group have enhanced the procedure. Now they can produce crystals of silicon carbide, which are 3-4 inch in size and with excellent characteristics.

Crystalline lattice of silicon carbide has about 160 modifications, which of those shows variations in semiconductor properties. Sometimes sandwich-like materials consisted of layers with different propertied are needed. Usually such “sandwiches” were made sticking a few plates together. The new technology enables growing monolithic crystal consisted of the required layers, but without splits between the layers.

According to the scientists, the cost of one plate of silicon carbide produced by the new technology may be ten times lower than the present costs.