Small signal modelling of GaN HEMT at 70GHz

A new 18-element small-signal model for GaN high electron mobility transistor is presented to operate at very high frequencies around 70 GHz. This model accounts for the need of a capacitor to represent the capacitive effect between the end of the drain electrode and contacting pad of the gate electrode. An extrinsic parasitic gate-drain capacitance as for higher frequencies this parameter becomes significant even under cold-FET conditions. This novel approach compensates for the high linear dependency of inductance at such high frequencies and the improved performance is evident in the S-parameter modelled. The validity of the proposed model has been well-illustrated up to 100 GHz frequency by the modelled S-parameters.