A High-Performance Depletion Mode Graded AlGaN/GaN HEMT with Trilayer Cap and AlInGaN Back Barrier for Analog and RF Applications

Abstract In this paper, a high-performance, depletion-mode GaN based High-Electron-Mobility Transistor (HEMT) is designed and investigated for analog and radio-frequency applications. In the proposed device, we have introduced a trilayer cap and a passivation-embedded T shaped partially recessed gate with a graded AlGaN barrier including Al₃₀Ga₇₀N, Al₂₅Ga₇₅N, and Al₂₀Ga₈₀N layers. In addition, an AlInGaN back barrier has been incorporated to enhance the analog and RF performance of the device. The graded AlGaN barrier enhances carrier transport, while the AlInGaN back barrier improves carrier confinement and suppresses leakage. The partially recessed T-shaped gate reduces gate resistance and strengthens channel control, whereas the (n-GaN)/(i-AlN)/(n-GaN) trilayer cap employed to strengthen conduction band bending and reduces gate leakage, resulting in improved analog and RF performance of the proposed device. Furthermore, simulation model validation is achieved by calibrating the simulations against experimental results, followed by an optimization approach based on the different Al compositions (10%, 15% & 20%) in the Al x In 0.15 Ga 1-x-0.15 N back-barrier (BB) layer. All analyses and results reported in this paper are obtained using Silvaco ATLAS TCAD simulations. Moreover, a possible step-by-step fabrication process for the proposed device has been illustrated to demonstrate its practical feasibility. The proposed device shows improved characteristics, including higher drain current (I DS ), transconductance (g m ), intrinsic gain(g m /g d ), transconductance generation factor (TGF), gain frequency product(GFP), early voltage(V EA ) , cut-off frequency (f T ), and maximum frequency (f MAX ) compared to the state of-the-art devices.