3D analysis of thermal and electrical performance of wide bandgap VDMOSFETs

Abstract

Power electronics is based on the conversion and conditioning of electric power in its different forms. The need for higher operating voltages, temperatures and switching speeds have necessitated for the use of semiconductor materials more superior to Silicon for power electronics purposes. Wide bandgap (WBG) materials like SiC, GaN and Diamond have been known to demonstrate better material properties as compared to Silicon, like higher operating temperatures, higher breakdown voltages and reduced thermal and electrical resistances which make them ideal for high power electronic devices. This paper analyzes the thermal and electrical performance of WBG power MOSFETs, in particular the Vertical Double-diffused MOSFET (VDMOSFET) structure, modeled in the commercial simulation software COMSOL Multiphysics. VDMOSFETs are ideal for high power electronic applications owing to their higher voltage blocking capabilities as compared to the conventional lateral MOSFET structure. COMSOL uses Finite Element/Volume Analysis methods to approximate solutions to differential equations involved with complex geometries and physics. The 3D model investigated in COMSOL for this paper solved for thermal and electrical variables for VDMOSFETs using SiC and GaN as their semiconductor material. Only a quarter of the 3D VDMOSFET structure was modeled for faster computational speed as the structure itself is symmetric about two vertical planes. The temperature profiles and current densities of each WBG material VDMOSFET were analyzed for different operating voltages. These profiles were compared with a Si VDMOSFET model to determine relative similarities and differences between each material.