2.5 A/mm/350 GHz aggressively scaled gate engineered Fe-doped AlN/GaN channel HEMT with graded InGaN Backbarrier on SiC-wafer for next generation RF power electronics applications

Abstract

This study intends to investigate the effects of barrier scaling, a crucial RF GaN-HEMT design element, which is imperative to achieve enhanced performance at nano-scale dimensions. From the performance characterization of the designed 50 nm recessed gated Fe-doped AlN/GaN/SiC HEMT featuring graded InGaN-back barrier (BB), the highest transconductance of 464.7 mS/mm, a maximum fT of 351.5 GHz, peak ID of 1.596 A/mm, & high drain saturation current of 2.527 A/mm at VGS = 3 V is observed for a 6 nm thin AlN barrier due to better gate control, and aided quantum well confinement because of Fe-doped buffer & graded InGaN BB. We observed that as barrier thickness increases, threshold voltage (Vth) becomes more negative and performance is deteriorated due to poor aspect ratio. This work also examines the role of gate-engineering on the electrical properties of the designed HEMT by employing different metals. The TCAD analysis indicates that the Al-gate HEMT had better DC/RF performance because of its lower ϕm (work-function). The performance declines and Vth increases as the Schottky barrier raises due touplifting of the conduction band edge. Since, it is crucial to understand the contribution of Rs & Rd in RF design, so in addition, we have done simulations by scaling source-gate gap (LGS), & drain-gate gap (LGD). It was found that the HEMT delivered better performance at the smallest LGS & LGD due to minimal Rs & Rd. The incredible performance of the novel HEMT reflects enhanced electron transport properties and implies that it possesses the capability of being extremely desirable for future aviation, military, and space applications.