20 kV, 2 cm2, 4H-SiC gate turn-off thyristors for advanced pulsed power applications

The development of high-voltage power devices based on wide bandgap semiconductor such as silicon carbide (SiC) has attracted great attention due to its superior material properties over silicon for high-temperature applications. Among the high-voltage SiC power devices, the 4H-SiC gate turn-off thyristor (GTO) offers excellent current handling, very high voltage blocking, and fast turn-off capabilities. The 4H-SiC GTO also exhibits lower forward voltage drop than the IGBT-based switches, resulting in lower losses during normal operation. It is an ideal switch for pulsed power applications that require high turn-on di/dt. In order to achieve a blocking capability of or greater than 20 kV in SiC, a thick drift epi-layer (> 160 μm) with an improved carrier lifetime (5 ~ 10 μs) is necessary to obtain a full conductivity modulation. In this paper, for the first time to our knowledge, we report our recently developed 1×2 cm², 20 kV, 4H-SiC p-GTO using a 160 μm, 2×10¹⁴/cm³ doped, p-type drift layer. The active conducting area of the device is 0.53 cm². Due to the limitations of the high-voltage test set-up, the 4H-SiC p-GTO showed an on-wafer gate-to-anode blocking voltage of 19.9 kV at a leakage current of 1 μA, which corresponds to a one-dimensional (1D) maximum electrical field of ~ 1.5 MV/cm at room-temperature. To measure this large area, 4H-SiC, p-GTO at high current levels (> 100 A/cm²), the forward characteristics of the device were evaluated using a Tektronix 371 curve tracer in pulse mode. A differential specific on-resistance of 11 MΩ-cm² was obtained at a gate current of 0.35 A and a high current of 300 A/cm2 ~ 400 A/cm². More results and discussion will be presented at the conference.

Source:IEEE

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