Wide Bandgap (WBG) semiconductor devices are becoming the simpler and cheaper option as compared to the limited capabilities of Si devices because of their better blocking voltages, switching frequencies, thermal conductivities and operating temperatures. WBG semiconductors like Gallium Nitride (GaN) have better materials properties specifically suited for high power and high frequency electronics and they are slowly being favored for such applications. GaN High Electron Mobility Transistors (HEMTs) have demonstrated superior performance characteristics as compared to Si Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) in terms of switching characteristics and switching losses. One particular GaN HEMT module investigated by the authors has been calculated to have less than five times the switching losses as compared to a similar Si MOSFET module under the same operating conditions. The use of the GaN module instead of Si module in an inverter application has also shown reduction of power losses and heatsink volume by 60% and 30% respectively for the GaN module. This paper investigates the effect of different heatsink materials (Aluminum, Copper, AlSiC and E-Material) on the overall temperature profile of the GaN module. The heatsink structure used for the simulations were obtained from commercially available straight-fin heatsink designs. Comparisons among these heatsink materials were done for the same operating and ambient conditions by simulating the combined HEMT-Heatsink structure in the Finite Element Analysis (FEA) software COMSOL Multiphysics. The simulation results indicated Copper to be the best heatsink material among the four materials tested.
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.
This paper investigates the thermal performance of different wide bandgap (WBG) materials for their applicability as
semiconductor material in power electronic devices. In particular, Silicon Carbide (SiC) and Gallium Nitride (GaN) are
modeled for this purpose. These WBG materials have been known to show superior intrinsic material properties as
compared to Silicon (Si), such as higher carrier mobility, lower electrical and thermal resistance. These unique properties
have allowed for them to be used in power devices that can operate at higher voltages, temperatures and switching
speeds with higher efficiencies. Digital prototyping of power devices have facilitated inexpensive and flexible methods
for faster device development. The commercial simulation software COMSOL Multiphysics was used to simulate a 2-D
model of MOSFETs of these WBG materials to observe their thermal performance under different voltage and current
operating conditions. COMSOL is a simulation software that can be used to simulate temperature changes due to Joule
heating in the case of power MOSFETs. COMSOL uses Finite Element/Volume Analysis methods to solve for variables
in complex geometries where multiple material properties and physics are involved. The Semiconductor and Heat
Transfer with Solids modules of COMSOL were used to study the thermal performance of the MOSFETs in steady state
conditions. The results of the simulations for each of the two WBG materials were compared with that of Silicon to
determine relative stability and merit of each material.