Large signal and analytic non-linear modelling of GaN HEMT-based varactors
Résumé
AlGaN/GaN hetero-structure varactors with various sizes have been fabricated and characterized in the large-signal regime to construct a non-linear model. A standard 0.5 \mum gate width GaN HEMT process was used to fabricate these varactors. The proposed large signal model maintains good accuracy up to 10 GHz and RF power levels up to 18 dBm. The Cmax/Cmin ratio for all devices is about 1.73 under small signal operation (below 5 dBm) and decreases to 1.25 at 18 dBm. This large signal model is described by an approximate analytical expression containing empirical coefficients which are introduced for the voltage and RF power dependency of capacitance. In addition, the analytical solution agrees remarkably well with the experimentally extracted C-V curves at various RF power levels and can be used as a general model to represent the nonlinear behavior of GaN based varactors devices. © 2019 IEEE.