SiC semiconductors in SiC power devices

SiC (Silicon Carbide) is a compound semiconductor material composed of Si (silicon) and C (carbon).

    Not only the insulation breakdown field strength is 10 times that of Si, and the band gap is 3 times that of Si, but the necessary p-type and n-type can be controlled in a wide range during device fabrication, so it is considered to be a kind of beyond the limit of Si. Power device materials.

    There are various polytypes (multiple crystals) in SiC, and their physical properties are also different.

    For the production of power devices, 4H-SiC is suitable.

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    2. Features of power devices

    The insulation breakdown field strength of SiC is 10 times that of Si. Therefore, compared with Si devices, a drift layer with a higher impurity concentration and a thinner thickness can be used to make a high withstand voltage power device of 600V to several thousandV.

    The impedance of a high withstand voltage power device is mainly composed of the impedance of the drift layer. Therefore, a high withstand voltage device with a very low on-resistance per unit area can be obtained by using SiC.

    Theoretically, for devices with the same withstand voltage, the resistance of the drift layer per unit area of SiC can be reduced to 1/300 of that of Si.

    In Si materials, in order to improve the on-resistance increase caused by high withstand voltage, minority carrier devices (bipolar transistors) such as IGBT (Insulated Gate Bipolar Transistor) are mainly used. Type device), but there is a problem of large switching loss, and the result is that the resulting heat will limit the high-frequency drive of the IGBT.

    However, SiC materials can achieve high withstand voltage with majority carrier devices (Schottky barrier diodes and MOSFETs) of high-frequency device structure, so as to achieve "high withstand voltage", "low on-resistance", and "high frequency" at the same time. "These three characteristics.

    In addition, the band gap is wider, three times that of Si, so SiC power devices can work stably even at high temperatures.