Abstract
In this simulation work, the effect of AlxGa1-xN and InxGa1-xN back barriers (BB) on the RF & DC performances of recessed T-gated Fe-doped AlN/GaN/SiC HEMT device is investigated. The novel HEMT achieved a peak GM of 435.9 mS/mm, the highest ID of 1.89 A/mm, and a maximum fT of 197.4 GHz with Al0.18Ga0.82N BB which can be attributed to enhanced mobility and carrier confinement in the quantum well (QW) due to the integration of BB, presence of Fe-doping in the GaN buffer in conjunction with recessed T-gate approach. On the other hand, the device with In0.20Ga0.80N BB recorded a peak GM of 434.9 mS/mm, a peak ID of 1.83 A/mm, and a maximum fT of 196.4 GHz. The flatness GM is attributable to the applied high drain bias of 5 V. The device performance deteriorated with an increase of Al and In mole fractions of the BB layers following an increased dislocation density which influenced the epitaxial quality of the heterostructures. This paper also investigates the impact of gate metals on the electrical performance of the Al0.18Ga0.82N and In0.20Ga0.80N BB devices. In both cases, the TCAD results revealed that the HEMT with lower ϕm (work function) gate metal i.e., Al-gate exhibited superior DC/RF performance. Owing to an uplift of the conduction band edge the performance degraded following the raise of the Schottky barrier that leads to the collection of the least number of carriers at the AlN/GaN interface hence resulting in poor sheet carrier density. Besides, the gate metal Pt with the highest work function of 5.65 eV is suitable to pursue E-Mode operation. In addition, the simulation to explore the impact of scaling source-drain spacing (LSD) revealed that limiting gate-to-drain distance (LGD) and gate-to-source distance (LGS) is the key to achieve enhance RF/DC performance. It is no surprise that this device is at the forefront of the future 5G/6G, military, defense, and RF power applications.
Published Version
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