Study on the Radio Frequency Performance of GaN High Electron Mobility Transistor With Multilayer Gradient AlGaN Barrier Layers and Novel Gate Air Cavities

This article proposes a novel high electron mobility transistor (HEMT) device with a triple‐barrier‐layer (TBL‐HEMT) structure of AlGaN. The conventional 15 nm single AlGaN barrier is divided into three sublayers with Al compositions of 0.25, 0.20, and 0.15 from top to bottom. In order to enhance radio frequency (RF) performance, a 1 μm linearly graded AlGaN underlying layer is employed to efficiently suppress short channel effect during device scaling. Three types of stacked passivation films including HfO ₂ /SiO ₂ , Al ₂ O ₃ /SiO ₂ , and SiO ₂ /SiO ₂ are analyzed, and a 100 nm air gap near the gate helps cut parasitic gate capacitance greatly. The optimized SiO ₂ /SiO ₂ (air = 100 nm) scheme delivers the highest cutoff frequency ( f _T ) of 114 GHz. The device under consideration in this article demonstrates a high cutoff frequency, excellent direct current performance, and a very high RF quality factor. These characteristics offer substantial reference value for future applications in the domain of RF electronics.