Physical model for GaN HEMT design optimization in high frequency switching applications

In this paper, physical modeling of a GaN HEMT is proposed, with the objective of device design optimization for application in a high frequency DC/DC converter. From the point of view of a switching application, physical model for input, output and reverse capacitance as well as for channel resistance is very important, since the aforementioned parameters determine power losses in the circuit. The obtained physical model of the switching device can be used for simulation models such as PSpice or hybrid behavioral power loss models for high frequency DC/DC converters. In this work, extrinsic model for I_d (V_ds, V_gs) output characteristics of a depletion mode GaN HEMT with a field plate structure was obtained, as well as physical model for input, output and reverse capacitance in the subthreshold regime. The model was implemented in Simplorer simulation model and verified by the measured efficiency curves of the buck converter prototype, using the GaN HEMT that was analyzed. With the increase of the switching frequency, precision of the model increases, especially in the low power area, which is the area of interest in our application.