IGBT Basic (6)

3-4. Leakage Current

Leakage current is divided into two types. One is leakage current from the depleted drift region, and the other flows on the surface of the junction termination.

Since the IGBT uses a P+ substrate and is irradiated with electrons to improve switching speed, the amount of leakage current from the drift region is greater than that of the power MOSFET. If there is a high voltage between the anode and cathode when the IGBT is off, the depletion region widens to nearly the entire drift region from the P+ body / N- drift junction (J2), and the entire region becomes depleted. The electron hole created by the heat of the depletion region is manifested as leakage current according to the area of the depletion region and minority carrier lifetime. This increases with the increase of the rated voltage and current. In particular, leakage current increases as the minority carrier lifetime shortens. As such, leakage current tends to increase with higher speed IGBTs.