Hervé Morel

This paper presents a high-voltage measurement probe based on the Pockels effect. The sensor provides galvanic isolation for electric field sensing, featuring an intrinsic bandwidth of 1 GHz. A key advantage is its inherent immunity to electromagnetic interference (EMI), which combined with galvanic isolation enables clean measurements in high-noise environments typical of wide-bandgap (WBG) device characterization. The probe integrates a planar capacitor-based electric-field-to-voltage transformer connected to the drain (D) and source sense (SS) contacts. This transformer is combined with a Pockels-effect sensor, enabling differential measurement of V_DS without direct electrical contact, thereby avoiding voltage limitations and bandwidth degradation. The probe performance is experimentally validated under transients up to 4 kV during silicon carbide (SiC) MOSFET avalanche under unclamped inductive switching (UIS) conditions. Results show excellent agreement with a passive reference probe and demonstrate a linear response from 0 V to 4 kV, validating the probe capability for accurate, high-speed, and high-voltage monitoring in power electronics applications.

This paper presents for the first time a comparison between experimental measurements of Optical Beam Induced Current (OBIC) and finite element simulations on high-voltage bipolar diodes. Two peripheral protection structures were chosen: a simple MESA protection and a MESA + JTE combination. Comparable experimental and simulated results were obtained in both cases.

In this paper, the static and dynamic characterization of a High Voltage (10kV) 4H-SiC Bipolar Junction Transistor (BJT) is presented. Using a high-voltage source in vacuum conditions, a breakdown voltage of 11 kV was measured. Results showed that both large and small BJTs exhibit similar on-state resistance per unit area and collector current density of 55 A.cm^-2. The current gain increases with a decrease in temperature, indicating reduced charge carrier recombination at lower thermal energies. Also, BJT have been characterized in switching mode at 1 kV. The study concludes that 4H-SiC BJT demonstrates promising electrical performance for high-efficiency applications in harsh environments.

To expedite testing, time-dependent dielectric breakdown (TDDB) analyses are conducted on commercial 4H-SiC mosfet s at high gate-to-source voltages ( $\bm {V_{GS}}$ ), under Fowler–Nordheim conduction only. However, as inferred, such conditions induce impact ionization-generated holes in the dielectric layer (SiO $\bm {_{2}}$ ), resulting in a state transition in the effective dipolar moment. This accelerates the SiO $\bm {_{2}}$ degradation leading to an overestimation of its intrinsic lifetime at typical $V_{GS}$ values for gate driving in power converters. To address this, a physics-based approach is proposed to design TDDB tests under such conditions and to correct the intrinsic lifetime prediction at nominal $\bm {V_{GS}}$ values, shortening the testing time by up to two orders of magnitude. Thus, the proposed method is a well-suited candidate to be considered in SiC power device qualification standards, still under development.

This article considers a robust output set-point tracking problem for an $m$ -terminal power flow controller (PFC) for meshed dc micro-grids. The PFC is a power electronics device used to control the power flow at a node in the meshed grid and may act as a dc circuit breaker. The system is modeled by state-space bilinear dynamics coupled with a polynomial output. In the proposed design, the plant is first extended with an integral action processing the regulation error. The cascaded model composed of the plant and the integrator is then stabilized using a saturated state-feedback law, designed with a forwarding approach. An anti-windup function is added to cope with transient saturations. A tuning method is proposed to set the controller gains along the available degrees of freedom with respect to a cost function. The stability of the closed loop is guaranteed for any compact set of initial conditions and for small parametric variations around the nominal set point. Experiments have been carried out and these properties are successfully assessed on a tenth-scale experimental setup.

Many kinds of defects are present in AlGaN/GaN-on-Si based power electronics devices. Their identification is the first step to understand and improve device performance. Electron traps are investigated in AlGaN/GaN-on-Si power diodes using deep level transient Fourier spectroscopy (DLTFS) at different bias conditions for two Schottky contact’s etching recipes. This study reveals seven different traps corresponding to point defects. Their energy level E_T ranged from 0.4 eV to 0.57 eV below the conduction band. Among them, two new traps are reported and are etching-related: D3 (E_T = 0.47–0.48 eV; σ ≈ 10⁻¹⁵ cm²) and D7 (E_T = 0.57 eV; σ = 4.45 × 10⁻¹² cm²). The possible origin of the other traps are discussed with respect to the GaN literature. They are proposed to be related to carbon and nitrogen vacancies or to carbon, such as C_N-C_Ga. Some others are likely due to crystal surface recombination, native defects or a related complex, or to the nitrogen antisite: N_Ga.

Many kinds of defects are present in the different layers of GaN-on-Si epitaxy. Their study is very important, especially because they play a significant role on the device characteristics. This paper investigates the cause of the temperature dependence of the output and Miller capacitance at three temperatures: 25 °C, 75 °C and 150 °C of GaN-on-Si power transistors. In particular, this study focuses on the temperature dependence of the depletion voltage seen in these characteristics due to the progressive depletion of the two-dimensional electron gas (2DEG) under the device field plates. First, variations of the epitaxial growth are studied, showing that the intrinsic carbon concentration does not play a significant role. Secondly, the deep acceptor trap origin of the temperature dependence is analyzed with a TCAD simulation study. Thirdly, by adjusting TCAD parameters and binding them with experimental concentrations to fit experimental data, trap properties were obtained. The comparison of these properties with the acceptor traps in the literature suggests that the origin is a gallium vacancy tied to oxygen atom(s) on the N site.