Investigation of MCT behaviour at low temperatures

Tests were performed on MOS-controlled thyristors (MCTs) operating at temperatures ranging from room temperature (298 K, 25°C) down to liquid-nitrogen temperature (77 K, -196°C). Since this is a preliminary study, the MCTs tested were not specifically designed designed for low-temperature operation. Standard diodes were also tested in this temperature range in order to compare the behavior of such a basically simple device to that of the MCT. V-on and I-on (related to MCT latching current and turn-on design), breakdown voltage, V-forward, and I-off time were measured for various devices under test. It was found that the changes with decreasing temperature of five parameters (V-on, I-on, V-forward, I-off time, and conduction phase angle reduction) can be at least partially compensated by reducing the radiation dose. The rates of change of parameters with temperature are considered; some are fairly linear, while others display abrupt changes at transition regions