Date of Award


Document Type


Degree Name



Electrical Engineering

First Advisor

Mohammad A. Matin

Second Advisor

David Gao

Third Advisor

Haluk Ogmen

Fourth Advisor

Yun Bo Yi


AlGaN, COMSOL, HEMT, Thermal simulation, VDMOSFET, Wide-bandgap


Wide Bandgap (WBG) semiconductors like Silicon Carbide (SiC), Gallium Nitride (GaN) and Aluminum Gallium Nitride (AlGaN) have superior material properties as compared to Silicon (Si) like higher electrical breakdown voltages and bandgap energies as well as lower leakage currents as compared to Si which make them ideal to operate at higher voltage with lower thermal losses. These properties make WBG materials ideal for power devices like Vertical Double-diffused Metal Oxide Semiconductor Field Effect Transistors (VDMOSFETs). The use of digital prototyping through computer simulation increases the speed and flexibility of the design iterations while reducing the cost and time required for the design process. COMSOL Multiphysics is a Finite Element Method simulation software that has capabilities of combining different physics interfaces to simulate the effects of multiple interdependent physical phenomena. The use of these materials in switching devices like VDMOSFETs have been modelled in COMSOL Multiphysics in 2D and 3D for the purposes of this research dissertation. The electrical and thermal advantages of WBG materials, specifically SiC, GaN and AlGaN, as compared to Si as semiconductor materials for VDMOSFET structures for the exact same VDMOSFET structures are demonstrated and quantified from the results obtained.

The inverter is the most important component in a Photo Voltaic (PV) system that needs to be improved. Transformerless inverters have higher efficiencies at lower weight and size specifications as compared to ones with transformers. A modified topology of a single phase transformerless inverter with new current paths and improved efficiencies is proposed and its performance is analyzed in PSIM software with Si and WBG material power switching devices. The advantages of the WBG devices over Si in terms of power losses are also exhibited in this research. The power losses obtained from the models in PSIM are then used as inputs to COMSOL models for temperature comparisons of the switching device modules. The improved temperature performance of the WBG devices are then demonstrated by the reduction in heatsink requirements as compared to identical Si switching modules.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.


Received from ProQuest

Rights holder

Mahesh B. Manandhar

File size

116 pgs

File format