RF Performance of GaN-on-Si Power eHEMTs: Experimental Characterization and Modeling, Accounting for Temperature Dependence

This work presents the experimental characterization and modeling of a power GaN-on-Si enhancement-mode High Electron Mobility Transistor (eHEMT) provided by STMicroelectronics (SGT120R65AL). A dedicated electro-thermal DC-RF bench and a custom Transistor Test Fixture (TTF) were developed to ensure precise biasing, thermal control, and RF measurements of the Device Under Test (DUT). The DC characterization encompassed a systematic measurement campaign over 24 bias points and various temperature conditions, with subsequent parameter extraction via an approximate Statz model. Bench-induced parasitic resistances were quantified and corrected, allowing accurate derivation of the output characteristics. For the RF analysis, raw scattering parameters were acquired up to 1 GHz and processed through a de-embedding procedure based on auxiliary boards and lossy transmission line models. From the de-embedded S-parameters, several Figures of Merit (FoMs) and parameters were derived, including transition frequency and maximum oscillation frequency. Starting from the de-embedded Y-parameters in the 1-100 MHz range, a linear model of the device was then identified and optimized, presenting a good agreement with experimental data and enabling reliable extraction of capacitances, gain, and stability factors. The results provide insight into the temperature-dependent RF behavior of GaN-on-Si power eHEMTs and establish a validated measurement and modeling methodology.