Physics and technology of gallium nitride materials for power electronics

Since decades, silicon (Si) is the “lord“ of microelectronics industry. However, to meet the current societal need of reducing the global energy consumption, the next generation of power devices will have to guarantee an improved energy efficiency with respect to the existing Si devices. For this purpose, the introduction of new semiconductors technologies has become mandatory. Owing to its outstanding physical and electronic properties, gallium nitride (GaN) and related alloys are promising materials that can find application in the fields of high-power and high-frequency electronics, with a high energy efficiency. However, several hurdles are still hindering the full exploitation of these materials. For that reason the scientific community working on GaN-based materials is intensively involved in the solution of a variety of physical and technological problems encountered in the fabrication of GaN devices. This keynote speech aims to give an overview on some selected scientific aspects of GaN technology for power electronics devices, with a special attention to the case of high electron mobility transistors (HEMTs). In particular, after an introduction on the fundamental physical properties of the material, emphasis will be given to the current transport at metal/GaN interfaces, considering either Ohmic and Schottky contacts, which are important bricks of any power device. Afterwards, the relevance of dielectrics for GaN, either as passivation or gate insulation layers, will be briefly highlighted. Finally, the possible approaches to control the two dimensional electron gas (2DEG) in AlGaN/GaN heterostructures and to fabricate normally-OFF HEMTs will be presented, thus being one of the most important challenges in GaN technology.