Electrothermal nonlinear FET modeling for spectral prediction

The origin, mechanisms, and modeling of nonlinearities responsible for spectral spreading are reviewed and discussed. Intermodulation distortion, responsible for spectral spreading, is affected by slow memory effects. Pulsed IV measurements are used to obtain model current equations that have appropriate steady-state quiescent bias dependences related to channel temperature and trap occupancy. Thermal resistance can be measured in silicon devices by using ambient temperature adjustments to measure channel temperature changes due to quiescent self-heating. The presence of trap states in GaN HEMTs makes the assessment of thermal resistance much more difficult; however, the presence of these effects can be determined by comparing two sets of IV curves taken from quiescent bias points of equal power dissipation. Results are presented showing accurate prediction of third-, fifth-, and seventh-order intermodulation projects using an electrothermal model for a power Si MOSFET.