Dependence of AM/PM non-linearity on source field-plate in GaN HEMTs

AM/PM non-linearity of GaN HEMTs is analyzed with the help of physics-based industry standard ASM-HEMT model. A commercial GaN HEMT device is modeled with ASM-HEMT model. Accurate large signal non-linear model is obtained. Next this calibrated model is used to analyze the AM/PM non-linearity. It is found that the non-linear source field-plate capacitance in GaN HEMTs has a large impact on its AM/PM behavior. This is due to the large drain-source Vds voltage swing at high output powers. Large Vds swings from few volts to above 100 V modulates the charge in source field-plate region. This causes capacitance due to the source field-plate to be highly nonlinear” in-turn affecting the AM/PM behavior of the device.