Soutenance de thèse : Florian RIGAUD-MINET

Experimental and Simulation Study of GaN Device Size Limitations for High Efficiency Power Converters

Doctorant : Florian RIGAUD-MINET

Laboratoire INSA : AMPERE
Ecole doctorale : ED160 : Electronique Electrotechnique Automatique

Nowadays the electrification of our society leads to a huge demand for technologies related to power conversion systems. Lateral Gallium Nitride (GaN) transistors made on silicon wafers were shown to be more adapted for high efficiency power conversion over their silicon counterparts in the mid-voltage range (100 V–1000 V) at a reasonable cost. The targeted power converters are phone or laptop chargers, on-board chargers in electric vehicles, datacenter power supplies, micro-inverters for photovoltaics and more- electric-aircraft power converters. Power transistor scaling may be interesting to improve converter efficiency. Indeed, it could on the one hand, reduce the transistor-related charges QXX decreasing the switching time and hence the switching losses or on the other hand, decrease the on-state static resistance RDS,ON. However, the scaling should also result in a reduction of the device breakdown voltage as well as a switching that is more sensitive to parasitics that may have disturbed its stability/losses.
In this thesis the electric field distribution management and the switching losses of  lateral 650 V rated GaN-on-Silicon power devices built at CEA-LETI are studied. To do so, an electrical and physical failure analysis was performed to identify the voltage limitation of lateral GaN-on-Si diode test vehicles with different layout and substrate connections. To study the electric field distribution by Technology Computer Assisted Design (TCAD) using Synopsys® SentaurusTM, the electric field variation should reproduce the experimental breakdown voltage. Thus, a buffer trap calibration method based on experimental protocols was initiated. Finally, a new hard switching characterization test bench was set up to study the transistor design and manufacturing process impact on the switching losses of lateral GaN-on-Si transistors. The results help to derive guidelines for the technology and design scaling of the future generations of fully recessed GaN-on-Si Metal Insulator Semiconductor High Electron Mobility Transistor (MIS-HEMT).