Research On New SiC Field Effect Power Transistor

With the power electronics technology and new energy developing rapidly,SiC material becomes a research hotspot due to its wide band gap,high critical electric field strength and excellent heat dissipation performance.The SiC power device is one of the important research contents in the field of semiconductor power device.Compared with traditional Si-based devices,SiC power devices have obvious advantages in energy loss and conversion,as well as operating frequency,which are the main power semiconductor devices for next-generation energy conversion.SiC power devices include vertical devices and lateral devices.The vertical devices sustain the block voltage by the thickness of the vertical drift region,which has high chip area utilization.The lateral devices sustain the block voltage by the length of the lateral drift region,so the chip area factor should be taken into account when designing.Both devices are committed to obtaining high breakdown voltage and low specific on-resistance,at the same time can achieve low switching loss,etc.In view of these problems,SiC power vertical and lateral devices are studied and analyzed,and improvement approaches are proposed for their structure and performance.The specific research work is arranged as follows:1.A new SiC JFET power device with integrated reverse Schottky freewheeling diode is proposed.Aiming at the problem that the traditional SiC JFET has no reverse recovery capability,the gate region of the traditional SiC JFET is divided into upper and lower halves,where the lower half is replaced by the source,and a Schottky is integrated on the sidewall of the channel region.The integrated barrier Schottky diode can realize the reverse conduction function of SiC JFET without increasing the additional cell area,and improve the performance of the structure.The numerical simulation results show that the breakdown voltage of the proposed structure is 1730 V,the specific on-resistance of is 2.71 m?·cm~2.Compared with the conventional SiC JFET,the numerical simulation results show that the gate-drain charge of the proposed structure is reduced by 72.91%.Switching losses are reduced by about 91%,and average gate drive power consumption is reduced by more than 36%over a frequency range of 10kHz to 400kHz.The results also show that the reverse turn-on voltage is 0.85 V with low reverse recovery time and reverse recovery charge.The research results have been published in the IEEE IEEE Transactions on Electron Devices,an important journal in the field of devices.2.A SiC LDMOSFET structure with large on-state density is proposed.The proposed structure adopts the RESURF(Reduced SURface Field)principle,and a p-top layer is set to the surface of the drift region.With the assistance of the source field plate and the drain field plate,the lateral electric field distribution on the surface of the structure is jointly optimized,the average electric field in the block state is increased,and the voltage that the drift region can handle per micrometer is increased.Besides,the doping concentration of the drift region is greatly improved.Compared with the traditional SiC LDMOSFET structure,a trench gate is added on the existence of the planar gate,which expands the current conduction paths of the structure.The proposed device achieves a breakdown voltage of 1358 V,the specific on-resistance is 2.89 m?·cm~2.The trade-off relationship between the breakdown voltage and the specific on-resistance has been improved.The switching characteristics of the proposed structure is close to that of traditional SiC LDMOSFET structure.