We investigated a methodology to design light-triggered thyristors thanks to TCAD. The simulation model accuracy, especially the holding current and the minimum incident light intensity to turn-on, were compared with experimental results. The influence of SiC epitaxial layer lifetime and the incident light properties (wavelength and intensity) on the optically triggered 4H-SiC thyristor characteristics have been studied by simulation. We considered the wavelength dependency of quantum efficiency, penetration depth and photon energy. The holding current and turn-on time depends on the lifetime. The minimum intensity to turn-on the device significantly depends on the wavelength. This intensity becomes less than 0.003 times when the wavelength changed from 380 nm to 325 nm. In addition, the breakover voltage is affected by the constant incident light even if the intensity is tiny.

Due to the high switching speed of Gallium Nitride (GaN) transistors, parasitic inductances have significant impacts on power losses and electromagnetic interferences (EMI) in GaN-based power converters. Thus, the proper design of high-frequency converters in a simulation tool requires accurate electromagnetic (EM) modeling of the commutation loops. This work proposes an EM modeling of the parasitic inductance of a GaN-based commutation cell on a printed circuit board (PCB) using Advanced Design System (ADS®) software. Two different PCB designs of the commutation loop, lateral (single-sided) and vertical (double-sided) are characterized in terms of parasitic inductance contribution. An experimental approach based on S-parameters, the Cold FET technique and a specific calibration procedure is developed to obtain reference values for comparison with the proposed models. First, lateral and vertical PCB loop inductances are extracted. Then, the whole commutation loop inductances including the packaging of the GaN transistors are determined by developing an EM model of the device’s internal parasitic. The switching waveforms of the GaN transistors in a 1 MHz DC/DC converter are given for the different commutation loop designs. Finally, a discussion is proposed on the presented results and the development of advanced tools for high-frequency GaN-based power electronics design.

In order to better predict the high frequency switching operation of transistors in power converters, the access elements of these devices like resistances and inductances must be accurately evaluated. This paper reports on the characterization of a gallium nitride (GaN) packaged power transistor using S-parameters in order to extract the parasitics stemming from ohmic contacts and packaging. As the transistor is encapsulated, a calibration technique is set using specific test fixtures designed on FR4 printed circuit board (PCB) in order to get the Sparameter in the transistor plane from the measured ones. The proposed method is based a modified "Cold FET" technique and off-state measurements. It is applied to a commercially-available enhancement mode GaN HEMT (High Electron Mobility Transistor). The extracted parasitic elements are compared to reference values given by the devices manufacturers. The impact of junction temperature on drain and source resistances is also evaluated. Finally, an electrothermal model of these parasitics is proposed.