Comparison of n and p channel IGTs

N-channel insulated gate transistors with 600V forward blocking capability and continuous current rating of 10A and 25A have been reported in 1983. For many applications, such as motor drives, it is highly desirable to use complementary devices. For this reason both n-channel and p-channel IGTs have been developed. Since the drift region is strongly modulated by the injection of a very high concentration of electrons or holes during forward conduction, the drift region resistance of p-channel IGT becomes equal to that of n-channel IGT. The trade-off between forward drop and turn-off time for p-channel IGTs is also compared to n-channel IGTs. It can be seen that the forward drop of p-channel devices increases at a faster rate with decreasing turn-off time than for n-channel. This phenomena can be explained by using a model for the IGT consisting of a MOSFET driving a wide base NPN transistor. As the lifetime is reduced by the electron radiation, the NPN gain decreases. This leads to an increase in the forward voltage drop at a faster rate for the p-channel IGT due to the lower mobility for holes. Details of this model and other device characteristics, such as latching current, forward conduction, switching speed and blocking capability will be provided at the conference.