Nonlinear analysis of GaN MESFETs with Volterra series using large-signal models including trapping effects

Nonlinearities in GaN MESFETs are reported using a large-signal physics-based model. The model accounts for the observed current collapse to determine the frequency dispersion of output resistance and transconductance. Calculated f_T and f_max of a 0.8 μm×150 μm GaN MESFET are 6.5 and 13 GHz, respectively, which are in close agreement with their measured values of 6 and 14 GHz, respectively. A Volterra-series technique is used to calculate size and frequency-dependent nonlinearities. For a 1.5 μm×150 μm FET operating at 1 GHz, the 1 dB compression point and output-referred third-order intercept point are 16.3 and 22.2 dBm, respectively. At the same frequency, the corresponding quantities are 19.6 and 30.5 dBm for a. 0.6 μm×150 μm FET. Similar improvements in third-order intermodulation for shorter gatelength devices are observed.