Abstract
This paper characterises the effects of frequency dispersion in laterally diffused metal-oxide semiconductor (LDMOS) from pulsed-S-parameter measurement. Using the calculated high-frequency drain current from measured data, we demonstrate that length of the lightly doped drain extension is directly proportional to the amount of current collapse at high frequency. To capture the frequency dispersion in a nonlinear model, a frequency-domain mapping technique is proposed to allow us to augment quasi-static nonlinear electrothermal models. The importance of including the dispersiveness is demonstrated through comparing a standard quasi-static model, the newly augmented model and on-wafer load-pull measurements. For a 5-mm, 500 m unit-gate-width transistor, we demonstrate that the quasi-static model over predicts the drain efficiency during large signal drive at P3dB by 9%. The new augmented model is able to predict the efficiency within 2% of the measured value.