Temperature is a critical parameter for the GaN HEMT as it sharply impacts the electrical characteristics of the device more than for SiC or Si MOSFETs. Either when designing a power converter or testing a device for reliability and robustness characterizations, it is essential to estimate the junction temperature of the device. For this aim, manufacturers provide compact models to simulate the device in SPICE-based simulators. These models provide the junction temperature, which is considered uniform along the channel. We demonstrate through two-dimensional numerical simulations that this approach is not suitable when the device undergoes high electrothermal stress, such as during short circuit (SC), when the temperature distribution along the channel is strongly not uniform. Based on numerical simulations and experimental measurements on a 650 V/4 A GaN HEMT, we derived a thermal network suitable for SPICE simulations to correctly compute the junction temperature and the SC current, even if not providing information about the possible failure of the device due to the formation of a local hot spot. For this reason, we used a second thermal network to estimate the maximum temperature reached inside the device, whose results are in good agreement with the experimental observed failures.

Neutrons can lead to significant failures in high-voltage power devices; this paper investigates the behavior of a silicon-power PiN diode when exposed to a 14 MeV neutron beam. We present a novel methodology that combines experimental characterization and numerical simulation to examine the effects of ionic species generated by neutron-induced nuclear reactions in semiconductor materials. Experimental measurements were conducted at the Frascati Neutron Generator to explore the device’s failure under controlled irradiation conditions. Subsequently, to comprehend the failure mechanism, a combined simulation approach was adopted. The G4SEE Monte Carlo toolkit was first employed to simulate the interaction of 14 MeV neutrons with the silicon semiconductor material; the resulting secondary particle data were then utilized in three-dimensional electrothermal simulations performed using Silvaco TCAD, leveraging the cylindrical symmetry of the unit cell. The numerical model was validated by comparing the simulation results with the experimental data obtained during the neutron irradiation campaigns. Our study revealed that the (α, ²⁵Mg) ion pair is one of the products of the nuclear reaction that interacts most significantly with the electric field within the intrinsic region of the device. This interaction at the critical bias voltage results in a single-event burnout of the diode, as confirmed by experimental observations and numerical analysis. Although the demonstration is based on a monoenergetic 14 MeV source, the methodology is general and can be extended to assess device response under realistic atmospheric neutron spectra.