Small-signal RF performance enhancement of GaN HEMT using a graded channel structure: A TCAD-to-circuit approach

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This work presents a systematic device-to-circuit framework for the design and analysis of a 2 GHz small-signal linear RF amplifier using a GaN HEMT. Physics-based TCAD simulations are employed to obtain the device characteristics, and the extracted scattering parameters and noise parameters are exported as Touchstone files for circuit-level implementation in AWR Microwave Office. The primary contribution lies in establishing a consistent methodology for translating device-level simulation data into RF circuit design. A comparative evaluation is carried out between graded channel GaN HEMT (GC HEMT) and conventional GaN HEMT (C HEMT) structures to assess their influence on amplifier performance. The RF amplifiers are designed using small signal S parameter analysis, considering both power matching and noise matching approaches. For the power matched RF amplifier design at 2 GHz, the GC HEMT based RF amplifier achieves a power gain of 17.1 dB, whereas the C HEMT RF amplifier yields a gain of 12.1 dB. For the noise matched low noise amplifier (LNA), the GC HEMT LNA achieves a gain of 14.2 dB with a noise figure of 0.55 dB, while the C HEMT LNA exhibits a gain of 8.4 dB and a noise figure of 1.04 dB. The results demonstrate that the proposed TCAD-to-circuit approach enables reliable integration of physics-based device modelling with RF amplifier design, providing an effective platform for evaluating GaN HEMT based circuits for S band microwave and satellite communication front-end applications.