The transition from traditional Silicon (Si) MOSFETs to Gallium Nitride (GaN) transistors in high-power applications highlights the need for improved thermal management due to GaN's faster switching speeds, higher power density, and reduced on-resistance. However, efficient heat dissipation is critical to leverage GaN technology effectively. This study examines two core objectives: First, it compares the contact resistance and thermal behavior of GaN transistors (EPC2302) with Si MOSFETs (Infineon BSC030N08NS5) across different pad configurations (single vs. multiple) and spacing distances (2mm, 5mm, and 10mm). The results of Task 1 reveal how these configurations impact power dissipation, thermal distribution, and current density, identifying optimal layout designs for both transistor types.