The student Ander Udabe Zabala obtained an EXCELLENT CUM LAUDE

The student Ander Udabe Zabala obtained an EXCELLENT CUM LAUDE

---

• Thesis title: Impact of Gallium Nitride Devices in Real Power Electronics Applications

Court:

• Presidency: Estanislao Oyarbide Usabiaga (Universidad de Zaragoza)
• Vocal: Joseba Arza Alonso (Ingeteam)
• Vocal: Carlos Bernal Ruiz (Universidad de Zaragoza)
• Vocal: Víctor Manuel López Martín (Ikerlan)
• Secretary:Gonzalo Abad Biain (Mondragon Unibertsitatea)

Abstract:

Power converters traditionally use Silicon (Si) transistors and diodes for the conversion and control of electrical energy. Decades of refinement of manufacturing processes have led to the production of Silicon with virtually no defects, enhancing current conduction, voltage blocking, heat dissipation, and switching speeds of Silicon devices. These improvements have resulted in more efficient converters with higher power densities. However, as the quality of Silicon approaches its practical limits, the material itself becomes the primary barrier to further improve the electrical and thermal characteristics of the devices. In this context, Gallium Nitride (GaN) and Silicon Carbide (SiC), also known as Wide BandGap (WBG) semiconductors, offer superior electrical and thermal properties, providing a better alternative to Silicon for power devices.

These WBG devices can operate at high switching dynamics, which leads to efficient switching transients. In this way, the converter can operate at high frequencies while keeping high efficiency levels and reducing the volume of passive components. However, these fast switching transients present a challenge for an industry whose knowledge is still based on the standards of Silicon devices. Currently, no standard current probe provides sufficient bandwidth and low enough insertion impedance to measure these fast switching transients in Double Pulse Tests (DPT). This makes switching energy measurements challenging, which are mandatory during the converter design process. Additionally, the high dv/dt and di/dt of Wide Bandgap devices make PCB optimizations mandatory to minimize parasitic capacitances and inductances, essential for reducing transistor losses and preventing Electromagnetic Interference (EMI) issues.

Despite these challenges, SiC MOSFETs and Schottky diodes have matured enough to replace IGBTs and diodes in certain applications, providing higher efficiency and power density levels. To make the adoption of these SiC devices easier, manufacturers have made SiC MOSFETs gate terminal voltage requirements compatible with IGBT standards. However, GaN transistors are several steps behind SiC devices in terms of standardization, regarding gate requirements, transistor structures, packaging and cooling systems among others, which makes their adoption challenging in power applications. Therefore, although GaN technology offers promising conduction and switching properties, its market penetration is lower than that of SiC devices. For this reason, the main objective of this thesis is to provide some solutions to the challenges that must be solved to fully exploit the advantages offered by Gallium Nitride devices.

The thesis is structured into two main sections. The first part provides a comprehensive review of current GaN devices, examining their physics and the different GaN device structures. In addition, this section includes both dynamic and static characterizations of commercially available GaN devices, ultimately leading to the development of a simulation model for the HD-GIT and SG p-GaN devices. The second part of this research work is focused on the switching loss evaluation by means of calorimetric methods. In this context, the impact of the PCB stray capacitances on the switching losses has been evaluated.