Barrier and channel thickness engineering to optimize fin height for enhancement mode Al0.3Ga0.7N/GaN FinHEMT

Abstract In this work, a thorough analysis of the Al 0.3 Ga 0.7 N/GaN FinHEMT structure has been performed using three‐dimensional numerical simulations to achieve enhancement mode (E‐mode) operation. In the proposed optimized structure, the fin height ( H Fin ) is comprised of 7 nm critical strained AlGaN barrier layer with 30% Al mole fraction and 63 nm GaN channel layer having a fixed fin width ( W Fin ) of 160 nm. The two‐dimensional electron gas (2DEG) concentration near the hetero interface is found to vary inversely with H Fin of the proposed structure. The 2DEG variation was compared between fin‐shaped full tri‐gate approach and variable side gate length tri‐gate design counterpart for a fixed H Fin of 70 nm. We achieved an improved threshold voltage of −0.2 V in the optimized H Fin structure as compared to −1.45 V obtained in the unoptimized structure as reported earlier. Further, upon decreasing W Fin to 40 nm in the same structure having optimized H Fin of 70 nm, an E‐mode operation was achieved with a positive threshold voltage of 0.4 V. The positive shift in threshold voltage is explained with the help of necessary energy band diagram.