GaN-Based High Electron Mobility Transistor

A next-generation of highly efficient power devices is under development, utilizing wide bandgap semiconductors, such as GaN and SiC. These materials are gaining traction as attractive alternatives to silicon due to their superior properties. GaN, in particular, has garnered significant interest due to its excellent characteristics, such as a high electric field, saturation velocity, electron mobility, and thermal stability. GaN-based High Electron Mobility Transistors (HEMTs) exhibit superior performance, enabling operation at higher currents, voltages, temperatures, and frequencies. As a result, they are well-suited for the next wave of high-efficiency power converters, including applications in electric vehicles, phone chargers, renewable energy systems, and data centers. This chapter aims to provide an overview of the technological and scientific aspects of current GaN HEMT technology, including normally-on and normally-off. It starts by summarizing recent semiconductor market advancements and key application areas. A comparison between GaN and other materials is then presented, followed by a principle of HEMT and calculations of bound charge. The chapter also delves into normally-off GaN HEMT technology, focusing on aspects, like the recessed gate technique, p-GaN gate, and fluorine implantation. Additionally, reliability concerns associated with GaN HEMTs, such as low positive threshold voltage, 2DEG degradation, leakage current, and different degradation types, are examined. Finally, the study touches upon the use of different normally-off techniques in combination form to improve device parameters, such as threshold voltage and 2DEG concentration.

Keywords: AlGaN, Bandgap, Barrier layer, Channel layer, E-mode, GaN, HEMT, Normally-off, Normally-on, Piezoelectric, Polarization.