Abstract
Today, the introduction of wide band gap (WBG) semiconductors in power electronics has become mandatory to improve the energy efficiency of devices and modules and to reduce the overall electric power consumption in the world. Due to its excellent properties, gallium nitride (GaN) and related alloys (e.g., AlxGa1−xN) are promising semiconductors for the next generation of high-power and high-frequency devices. However, there are still several technological concerns hindering the complete exploitation of these materials. As an example, high electron mobility transistors (HEMTs) based on AlGaN/GaN heterostructures are inherently normally-on devices. However, normally-off operation is often desired in many power electronics applications. This review paper will give a brief overview on some scientific and technological aspects related to the current normally-off GaN HEMTs technology. A special focus will be put on the p-GaN gate and on the recessed gate hybrid metal insulator semiconductor high electron mobility transistor (MISHEMT), discussing the role of the metal on the p-GaN gate and of the insulator in the recessed MISHEMT region. Finally, the advantages and disadvantages in the processing and performances of the most common technological solutions for normally-off GaN transistors will be summarized.
Highlights
Nowadays, one of the most important societal challenges is represented by the steady increase of the energy consumption in the world
4H-SiC [3] is mature in terms of crystalline quality and available device performances, gallium nitride (GaN) is still affected by several materials and technology concerns, limiting its full exploitation in power electronics applications [4]
As recently reported by several market analysts, GaN is better suited for the low-medium voltage range (200–600 V), which includes a large portion of the consumer electronic market
Summary
One of the most important societal challenges is represented by the steady increase of the energy consumption in the world. Power electronics systems are used to provide the optimal characteristics of electric power (i.e., current, voltage, frequency, etc.) for any targeted application. Today the continuous demand for higher current, voltage and power density capability, as well as the need of a better energy efficiency to reduce the global energy consumption, are the driving forces to introduce new semiconductor technologies in power electronics and to overcome the inherent limitations of Si-based devices. Wide band gap (WBG) semiconductors, like silicon carbide (4H-SiC) and gallium nitride (GaN), are considered the best materials for the future energy efficient power electronics [2]. 4H-SiC [3] is mature in terms of crystalline quality and available device performances, gallium nitride (GaN) is still affected by several materials and technology concerns, limiting its full exploitation in power electronics applications [4]. The emphasis will be put on the p-GaN gate and on the recessed gate hybrid metal insulator semiconductor high electron mobility transistor (MISHEMT) approaches, which are the most widely adopted technologies at either R&D or commercial level
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