Over the last decade, gallium nitride (GaN) has emerged as an excellent material for the fabrication of power devices. Among the semiconductors 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 spontaneous 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 properties 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.

We present a comprehensive review and outlook of silicon carbide (SiC) and gallium nitride (GaN) transistors available on the market for current and next-generation power electronics. Material properties and structural differences among GaN and SiC devices are first discussed. Based on the analysis of different commercially available GaN and SiC power transistors, we describe the state-of-the-art of these technologies, highlighting the preferential power conversion topologies and the key characteristics of each technological platform. Current and future fields of application for GaN and SiC devices are also reviewed. The article also reports on the main reliability aspects related to both technologies. For GaN HEMTs, threshold voltage stability, dynamic ON-resistance, and breakdown limitation are described, whereas for SiC MOSFETs the analysis also focuses on gate oxide failure and short-circuit (SC) robustness. Finally, we give an overview on the perspective of such materials in different fields of interest. An indication of possible future improvements and developments for both technologies is drawn. The requirements for hybrid converters, along with a careful optimization of performance and the use of innovative optimization tools, are underlined.

Herein, the main factors and mechanisms that limit the reliability of gallium nitride (GaN)‐based light‐emitting diodes (LEDs) are reviewed. An overview of the defects characterization techniques most relevant for wide‐bandgap diodes is provided first. Then, by introducing a catalogue of traps and deep levels in GaN and computer‐aided simulations, it is shown which types of defects are more detrimental for the radiative efficiency of the devices. Gradual degradation mechanisms are analyzed in terms of their specific driving force: a separate analysis of recombination‐enhanced processes, driven by nonradiative recombination and/or temperature‐assisted processes, such as defects or impurity diffusion, is presented. The most common lifetime estimation methods and standards adopted for solid‐state luminaires are also reported on. Finally, the paper concludes by examining which are the typical degradation and failure mechanisms exhibited by LEDs submitted to electrical overstress.

This paper presents an extensive analysis of the operating principles, theoretical background, advantages and limitations of laser-based lighting systems. In the first part of the paper we discuss the main advantages and issues of laser-based lighting, and present a comparison with conventional LED-lighting technology. In the second part of the paper, we present original experimental data on the stability and reliability of phosphor layers for laser lighting, based on high light-intensity and high-temperature degradation tests. In the third part of the paper (for the first time) we present a detailed comparison between three different solutions for laser lighting, based on (i) transmissive phosphor layers; (ii) a reflective/angled phosphor layer; and (iii) a parabolic reflector, by discussing the advantages and drawbacks of each approach. The results presented within this paper can be used as a guideline for the development of advanced lighting systems based on laser diodes.

Application of gallium nitride high-electron-mobility transistors (GaN HEMTs) to millimeter-wave power amplifiers requires gate length scaling below 150 nm: in order to control short-channel effects, the gate-to-channel distance must be decreased, and the device epitaxial structure has to be completely redesigned. A high 2-D electron gas (2DEG) carrier density can be preserved even with a very thin top barrier layer by substituting AlGaN with AlN, InAl(Ga)N, or ScAlN. Moreover, to prevent interaction of hot electrons with compensating impurities and defects in the doped GaN buffer, the latter has to be separated from the channel by a back barrier. Other device designs consist in adopting a graded channel (which controls the electric field) or to adopt nitrogen-polar (N-polar) GaN growth (which decreases the distance between gate and channel, thus attenuating short-channel effects). The aim of this article is to review the various options for controlling short-channel effects, improve off-state characteristics, and reduce drain–source leakage current. Advantages and potential drawbacks of each proposed solution are analyzed in terms of current collapse (CC), dispersion effects, and reliability.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent of COVID-19, which has affected the international healthcare systems since the beginning of 2020. Among sanitizing approaches, UV irradiation is a well-known technology often used in different environments to reduce the microbial contamination and the viral transmission. In particular, several works have demonstrated that UVC radiation is able to inactivate SARS-CoV-2 compromising its viral genome and virion integrity. With this work we review and analyze the current status of the pandemic and the state of the art of the UV technology. With traditional UVC discharge lamps having a serious environmental issue, due to their working principle based on mercury, a primary focus is shifted on the aluminum gallium nitride based deep-ultraviolet light emitting diodes. These devices are exploited for compact and environmentally friendly disinfection systems, but efficiency and reliability still play a limiting role into their mass market adoption and system efficacy. In this work we then analyze the latest reports on the effects of dose and wavelength on viral inactivation, thus providing two key pillars for the development of UVC based disinfection systems: the status of the technology and a quantitative evaluation of the dose required to achieve an effective coronavirus inactivation.