Vertical GaN MOSFET Power Devices.

Gallium nitride (GaN) possesses remarkable characteristics such as a wide bandgap, high critical electric field, robust antiradiation properties, and a high saturation velocity for high-power devices. These attributes position GaN as a pivotal material for the development of power devices. Among the various GaN-based devices, vertical GaN MOSFETs stand out for their numerous advantages over their silicon MOSFET counterparts. These advantages encompass high-power device applications. This review provides a concise overview of their significance and explores their distinctive architectures. Additionally, it delves into the advantages of vertical GaN MOSFETs and highlights their recent advancements. In conclusion, the review addresses methods to enhance the breakdown voltage of vertical GaN devices. This comprehensive perspective underscores the pivotal role of vertical GaN MOSFETs in the realm of power electronics and their continual progress.

Improving the High-Temperature Gate Bias Instabilities by a Low Thermal Budget Gate-First Process in p-GaN Gate HEMTs.

In this study, we report a low ohmic contact resistance process on a 650 V E-mode p-GaN gate HEMT structure. An amorphous silicon (a-Si) assisted layer was inserted in between the ohmic contact and GaN. The fabricated device exhibits a lower contact resistance of about 0.6 Ω-mm after annealing at 550 °C. In addition, the threshold voltage shifting of the device was reduced from -0.85 V to -0.74 V after applying a high gate bias stress at 150 °C for 10-2 s. The measured time to failure (TTF) of the device shows that a low thermal budget process can improve the device's reliability. A 100-fold improvement in HTGB TTF was clearly demonstrated. The study shows a viable method for CMOS-compatible GaN power device fabrication.

State-of-the-Art ß-Ga2O3 Field-Effect Transistors for Power Electronics.

Due to the emergence of electric vehicles, power electronics have become the new focal point of research. Compared to commercialized semiconductors, such as Si, GaN, and SiC, power devices based on ß-Ga2O3 are capable of handling high voltages in smaller dimensions and with higher efficiencies, because of the ultrawide bandgap (4.9 eV) and large breakdown electric field (8 MV cm-1). Furthermore, the ß-Ga2O3 bulk crystals can be synthesized by the relatively low-cost melt growth methods, making the single-crystal substrates and epitaxial layers readily accessible for fabricating high-performance power devices. In this article, we first provide a comprehensive review on the material properties, crystal growth, and deposition methods of ß-Ga2O3, and then focus on the state-of-the-art depletion mode, enhancement mode, and nanomembrane field-effect transistors (FETs) based on ß-Ga2O3 for high-power switching and high-frequency amplification applications. In the meantime, device-level approaches to cope with the two main issues of ß-Ga2O3, namely, the lack of p-type doping and the relatively low thermal conductivity, will be discussed and compared.

Gateway towards recent developments in quantum dot-based light-emitting diodes.

Quantum dots (QDs), with their excellent photoluminescence, narrow emission linewidth, and wide color coverage, provide unrivaled advantages for advanced display technologies, enabling full-color micro-LED displays. It is indeed critical to have a fundamental understanding of how QD properties affect micro-LED display performance in order to develop the most energy-efficient display device in the near future. However, to take a more detailed look at the stability issues and passivation ways of QDs is essential for accelerating the commercialization of QD-based LED technologies. Knowing about the most recent breakthroughs in QD-based LEDs can give a good indication of how they might be used in shaping the future of displays. In this review, we discuss the characteristics of QD-based LEDs for the applications of display and lighting technologies. Various approaches for synthesis and the stability improvement of QDs are addressed in detail, along with recent advancements towards QD-based LED breakthroughs. Moreover, we summarize our latest research findings in QD-based LEDs, providing valuable information about the potential of QD-based LEDs for future display technologies.

Development of GaN HEMTs Fabricated on Silicon, Silicon-on-Insulator, and Engineered Substrates and the Heterogeneous Integration.

GaN HEMT has attracted a lot of attention in recent years owing to its wide applications from the high-frequency power amplifier to the high voltage devices used in power electronic systems. Development of GaN HEMT on Si-based substrate is currently the main focus of the industry to reduce the cost as well as to integrate GaN with Si-based components. However, the direct growth of GaN on Si has the challenge of high defect density that compromises the performance, reliability, and yield. Defects are typically nucleated at the GaN/Si heterointerface due to both lattice and thermal mismatches between GaN and Si. In this article, we will review the current status of GaN on Si in terms of epitaxy and device performances in high frequency and high-power applications. Recently, different substrate structures including silicon-on-insulator (SOI) and engineered poly-AlN (QST®) are introduced to enhance the epitaxy quality by reducing the mismatches. We will discuss the development and potential benefit of these novel substrates. Moreover, SOI may provide a path to enable the integration of GaN with Si CMOS. Finally, the recent development of 3D hetero-integration technology to combine GaN technology and CMOS is also illustrated.

The Evolution of Manufacturing Technology for GaN Electronic Devices.

GaN has been widely used to develop devices for high-power and high-frequency applications owing to its higher breakdown voltage and high electron saturation velocity. The GaN HEMT radio frequency (RF) power amplifier is the first commercialized product which is fabricated using the conventional Au-based III-V device manufacturing process. In recent years, owing to the increased applications in power electronics, and expanded applications in RF and millimeter-wave (mmW) power amplifiers for 5G mobile communications, the development of high-volume production techniques derived from CMOS technology for GaN electronic devices has become highly demanded. In this article, we will review the history and principles of each unit process for conventional HEMT technology with Au-based metallization schemes, including epitaxy, ohmic contact, and Schottky metal gate technology. The evolution and status of CMOS-compatible Au-less process technology will then be described and discussed. In particular, novel process techniques such as regrown ohmic layers and metal-insulator-semiconductor (MIS) gates are illustrated. New enhancement-mode device technology based on the p-GaN gate is also reviewed. The vertical GaN device is a new direction of development for devices used in high-power applications, and we will also highlight the key features of such kind of device technology.