GaN-based power devices: Physics, reliability, and perspectives

TLDR

Gallium nitride has emerged as an excellent material for power devices, offering the widest bandgap, largest critical field, and highest saturation velocity among market‑available semiconductors, enabling high‑speed/high‑voltage components. The tutorial aims to understand and describe trapping and degradation processes in GaN to optimize device stability and reliability, offering guidance on the physics, technology, and reliability of GaN‑based power devices. The authors explain that spontaneous and piezoelectric polarization in AlGaN/GaN heterostructures forms a high‑mobility two‑dimensional electron gas, while vertical and three‑dimensional device architectures (fin, trench, nanowire) are explored for high‑power/high‑voltage operation, and they analyze the physical origins of traps and degradation mechanisms to assess reliability. GaN transistors achieve low resistive and switching losses thanks to high‑mobility 2DEG and small parasitic capacitances, and device scaling with monolithic integration enables high‑frequency operation and miniaturization, providing a comprehensive overview of current and next‑generation GaN electronics.

Abstract

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.