Graduation Semester and Year




Document Type


Degree Name

Master of Science in Mechanical Engineering


Mechanical and Aerospace Engineering

First Advisor

Dereje Agonafer


Gallium Nitride (GaN) is a binary III/V wide band gap semiconductor used in power electronics for operations at high power densities and high speeds. GaN has excellent characteristics like high break-down voltage, high thermal conductivity, and high electron saturation velocity which have led to an intensive study and wide use of GaN in many fields. Some of these fields range from amplifiers, MMIC, laser diodes, pulsed radars and counter-IED jammers to CAT-V modules and fourth generation infrastructure base-stations. Currently GaN devices suffer from high temperature due to self-heating which reduces the mean time to failure. In this study package level thermal analysis and management of GaN high electron mobility transistor package was carried out for determination of maximum junction temperature and junction-case thermal resistance (Rjc). Two Quad Flat No Lead models with different host substrate namely SiC and Si are used for analysis. The model takes into account the thickness of GaN and host substrate layers, the gate pitch, length, width, and thermal conductivity of GaN, and host substrate. A parametric study is being carried out to optimize and reduce the maximum junction temperature and junction to case thermal resistance (Rjc) by providing convective air cooling and heat sink. The other part of this study includes optimization of the model using diamond as the host substrate and ceramic as mold compound material to monitor the decrease in the thermal resistance value. Comparative results in this study show the percentage reduction in the estimated Rjc value. Thermal resistance value is estimated using the below formula, Rjc = Tj - Tc / P From the results obtained a significant reduction in the estimated Rjc value was observed when compared for no flow, air flow with heat-sink, different host substrate and different mold compound material conditions. In conclusion GaN HEMT can be optimized to achieve a significant improvement in operation. This would allow operation of GaN devices at high temperature without damaging the reliability and operation life-span.


Gallium Nitride, Thermal resistance, Optimization


Aerospace Engineering | Engineering | Mechanical Engineering


Degree granted by The University of Texas at Arlington