Structure Design And Performance Research Of MCT Device Based On Schottky Contact

The advancement of power devices is the foundation of the development of power electronic technology.New power devices and advanced power integrated circuits can greatly improve the power density and reliability of power electronic systems.Insulated gate field controlled thyristor(MOS Controlled Thyristor,MCT)as a basic high-power device,are widely used in various high-power power electronic systems.With the development of power electronic systems towards high integration,high power and high frequency,new requirements are placed on the electrical performance and reliability of power devices.Traditional MCT devices are no longer capable of increasingly updated power electronic circuits.New semiconductor materials and device fabrication processes broaden the structural design of MCT devices and provide new opportunities for improving the electrical performance and reliability of MCT.In this thesis,the structure and performance of a schottky-based MCT device are designed and studied.The research works are as follows:(1)Exploring the relationship between the structure and performance of MCT,a basic MCT simulation model C-MCT with field stop layer(N FS layer)and cathode short-circuit structure was developed.By adjusting the internal structural parameters of the device,the trade-off relationship between the normally-off characteristics and the turn-on characteristics of the MCT device was optimized.The blocking and conduction characteristics of C-MCT devices were calculated,and the correctness of the C-MCT model was verified by combining the operation analysis of MCT devices,which is ready for the design of new MCT structures.(2)The MCT device based on Schottky was designed: Combined with the theory of Schottky barrier,a new MCT device S-MCT was designed based on the C-MCT device model.By analyzing the circuit structure of S-MCT,the influence of Schottky barrier on its operation is obtained.The threshold voltage and saturation current of the internal MOS turn-off MOS were measured innovatively,the influence of the Schottky barrier on the MOS part of the MCT device was characterized by the induced potential.Through simulation calculations,the basic performance differences of the S-MCT devices and CMCT devices were compared,and the influence of Schottky barrier on the overall performance of MCT devices was summarized.(3)The dynamic characteristics of S-MCT was investigated: Two S-MCT dynamic simulation test circuits with inductive load and oscillating capacitive load circuit were built in Silvcao software platform.The influence of Schottky contact on device turn-on delay,turn-off delay,power loss and maximum turn-off current density were analysed and summarised.It demonstrated that S-MCT can shut off the circuit with current oscillation faster,and also the effect of the Schottky barrier to alleviate the current concentration when the MCT device is turned off.Its mechanism is explained in detail by the semiconductor conduction principle and simulation data.