High Performance Wide Bandgap Power Devices Characterization with a Focus on SiC Devices

High-performance Silicon Carbide (SiC) and Gallium Nitride (GaN) semiconductor power devices are subjected to intense research and are steadily expanding their presence in the market, as they allow for very efficient power conversion systems, fundamental for a more sustainable future. This dissertation focuses on the reliability of such devices, under high-stress conditions, analyzing trapping dynamics and degradation mechanisms, specifically what is related to impact-ionization, recombination-enhanced degradation and avalanche. This is necessary to allow these innovative devices to be used in ever higher power scenarios, where the greatest energy savings can occur. For SiC MOSFETs, the study analyzes the gate stack, describing charge generation, trapping, and detrapping phenomena occurring under high bias. Starting from the non-monotonic threshold voltage shift observed in the literature, due to electron trapping and hole generation, this study exploits mathematical models to demonstrate that holes are captured at deep levels and released through non-spontaneous trap-assisted processes. Recombination phenomena, confirmed by electroluminescence, are shown in this study to contribute to sample degradation during constant gate current stresses and Gate Switching Instability (GSI) stresses, both extensively performed on different samples. Degradation is characterized with charge pumping measurements, and it is shown to be occurring mainly at the oxide-semiconductor interface, while in the oxide, charge generation and trapping play the major role. As a last topic for SiC, current decay over time during Time-Dependent Dielectric Breakdown (TDDB) stresses is proven with a mathematical model to be linked to electron trapping at near-interfacial trap sites, that widens the Fowler-Nordheim tunneling barrier. In the GaN domain, a SPICE-based simulation methodology for Unclamped Inductive Switching (UIS) stresses is developed, clarifying how circuit and device parameters can prevent avalanche behavior, showing capacitive resonance instead. This model reproduces both ideal and non-ideal scenarios, helping to interpret measured data and device failure mechanisms, with the ultimate goal of giving manufacturing indications for devices improvement. Overall, this work provides novel contributions in understanding of degradation processes in SiC and helps identifying performance-limiting factors for GaN devices, improving reliability and performance of this crucial category of electron devices.