Analysis of the carrier and temperature distributions in gate turn-off thyristors by internal laser deflection

To achieve high breakdown voltages, power devices require a thick silicon layer with high resistivity. There are different concepts relating to how the electrical data of the devices can be optimized by a vertical inhomogenous carrier lifetime reduction in this region. Therefore, the measurement of the vertical and lateral carrier distribution in the on-state and during turn-on and turn-off would be very helpful to verify such ideas. In this paper we present a recently developed technique to measure the carrier concentrations and the temperature profiles simultaneously within the active region of power devices. The method is applied to gate turn-off thyristors (GTO) to study the influence of carrier lifetime reduction by irradiation with high-energy electrons or helium ions.