STUDY OF RADIATION EFFECTS IN GAN-BASED DEVICES

Radiation tolerance of wide-bandgap Gallium Nitride (GaN) high-electron-mobility transistors (HEMT) has been studied, including X-ray-induced TID effects, heavy-ion-induced single event effects, and neutron-induced single event effects. Threshold voltage shift is observed in X-ray irradiation experiments, which recovers over time, indicating no permanent damage formed inside the device. Heavy-ion radiation effects in GaN HEMTs have been studied as a function of bias voltage, ion LET, radiation flux, and total fluence. A statistically significant amount of heavy-ion-induced gate dielectric degradation was observed, which consisted of hard breakdown and soft breakdown. Specific critical injection level experiments were designed and carried out to explore the gate dielectric degradation mechanism further. Transient device simulations determined ion-induced peak transient electric field and duration for a variety of ion LET, ion injection locations, and applied drain voltages. Results demonstrate that the peak transient electric fields exceed the breakdown strength of the gate dielectric, leading to dielectric defect generation and breakdown. GaN power device lifetime degradation caused by neutron irradiation is reported. Hundreds of devices were stressed in the off-state with various drain voltages from 75 V to 400 V while irradiated with a high-intensity neutron beam. Observing a statistically significant number of neutron-induced destructive single-event-effects (DSEEs) enabled an accurate extrapolation of terrestrial field failure rates. Nuclear event and electronic simulations were performed to model the effect of terrestrial neutron secondary ion-induced gate dielectric breakdown. Combined with the TCAD simulation results, we believe that heavy-ion-induced SEGR and neutron-induced SEGR share common physics mechanisms behind the failures. Overall, experimental data and simulation results provide evidence supporting the idea that both radiation-induced SBD and HBD are associated with defect-related conduction paths formed across the dielectric, in response to radiation-induced charge injection. A percolation theory-based dielectric degradation model is proposed, which explains the dielectric breakdown behaviors observed in heavy-ion irradiation experiments

Neutron Induced Single-Event-Effects in Gallium-Nitride High Electron Mobility Transistors

This work is focused on the study of radiation-induced, especially neutron induced, single event effects in normally off gallium nitride high electron mobility transistors (GaN HEMTs). Normally off gallium nitride high power transistors have been commercially available on the market for a short number of years. Due to a large bandgap between conduction and valence band, this semiconductor material is inherently more resistant to failure due to induced charge carriers. In particular, the sensitivity to charge introduced by single particles has thus far only been investigated briefly. The knowledge about the reliability of the devices against radiation effects is important to ensure the reliability and functionality for safetyrelevant applications in space as well as on Earth. At this point in time, no protocols for testing GAN HEMTs on radiation hardness and single event effects have been published. In this study, three commercially available gallium nitride high electron mobility transistors of different device designs were investigated and compared with respect to their sensitivity to single event effects caused by radiation, especially neutrons. For this purpose, the devices under test were irradiated with the same assembly using five different types of particles and measured online. Irradiation was performed using high-energy xenon ions, ultra-high-energy lead ions, high-energy protons, monoenergetic neutrons and neutrons whose energy is similar to the atmospheric spectrum. The devices were irradiated with drain voltage applied but blocked and for each measured device the leakage current between drain and source as well as gate and source were recorded, likewise failures of the devices due to short circuit were registered. From the measurement data it was possible to determine the failure rate and the cross section for Single Event Effects due to particle ion interactions. Furthermore, the dependence of the failure rate on the energy deposition in the material and the comparability of proton and monoenergetic neutron measurements with the failure rate due to atmospheric neutrons were investigated. By observing gate and drain leakage current, two different failure mechanisms could be observed. In this work, no failures below 60% of the nominal drain voltage and 50% of the measured breakdown voltage of the devices were observed. Summarized and interpreted in the context of previous measurements, no inherent radiation hardness of the investigated gallium nitride high electron mobility transistors over comparable silicon or silicon carbide transistors could be shown for single particle effects

Challenges and New Trends in Power Electronic Devices Reliability

The rapid increase in new power electronic devices and converters for electric transportation and smart grid technologies requires a deepanalysis of their component performances, considering all of the different environmental scenarios, overload conditions, and high stressoperations. Therefore, evaluation of the reliability and availability of these devices becomes fundamental both from technical and economicalpoints of view. The rapid evolution of technologies and the high reliability level offered by these components have shown that estimating reliability through the traditional approaches is difficult, as historical failure data and/or past observed scenarios demonstrate. With the aim topropose new approaches for the evaluation of reliability, in this book, eleven innovative contributions are collected, all focusedon the reliability assessment of power electronic devices and related components

Feature Papers in Electronic Materials Section

This book entitled "Feature Papers in Electronic Materials Section" is a collection of selected papers recently published on the journal Materials, focusing on the latest advances in electronic materials and devices in different fields (e.g., power- and high-frequency electronics, optoelectronic devices, detectors, etc.). In the first part of the book, many articles are dedicated to wide band gap semiconductors (e.g., SiC, GaN, Ga2O3, diamond), focusing on the current relevant materials and devices technology issues. The second part of the book is a miscellaneous of other electronics materials for various applications, including two-dimensional materials for optoelectronic and high-frequency devices. Finally, some recent advances in materials and flexible sensors for bioelectronics and medical applications are presented at the end of the book

GaN-based power devices: Physics, reliability, and perspectives

Over the last decade, gallium nitride (GaN) has emerged as an excellent material for the fabrication of power devices. Among the semicon- ductors for which power devices are already available in the market, GaN has the widest energy gap, the largest critical field, and the highest saturation velocity, thus representing an excellent material for the fabrication of high-speed/high-voltage components. The presence of spon- taneous and piezoelectric polarization allows us to create a two-dimensional electron gas, with high mobility and large channel density, in the absence of any doping, thanks to the use of AlGaN/GaN heterostructures. This contributes to minimize resistive losses; at the same time, for GaN transistors, switching losses are very low, thanks to the small parasitic capacitances and switching charges. Device scaling and monolithic integration enable a high-frequency operation, with consequent advantages in terms of miniaturization. For high power/high- voltage operation, vertical device architectures are being proposed and investigated, and three-dimensional structures—fin-shaped, trench- structured, nanowire-based—are demonstrating great potential. Contrary to Si, GaN is a relatively young material: trapping and degradation processes must be understood and described in detail, with the aim of optimizing device stability and reliability. This Tutorial describes the physics, technology, and reliability of GaN-based power devices: in the first part of the article, starting from a discussion of the main proper- ties of the material, the characteristics of lateral and vertical GaN transistors are discussed in detail to provide guidance in this complex and interesting field. The second part of the paper focuses on trapping and reliability aspects: the physical origin of traps in GaN and the main degradation mechanisms are discussed in detail. The wide set of referenced papers and the insight into the most relevant aspects gives the reader a comprehensive overview on the present and next-generation GaN electronics

Reliability Analysis of Electrotechnical Devices

This is a book on the practical approaches of reliability to electrotechnical devices and systems. It includes the electromagnetic effect, radiation effect, environmental effect, and the impact of the manufacturing process on electronic materials, devices, and boards