Thermal Memory Effects on the Linearity of a GaAs PHEMT

This paper presents a comprehensive treatment of the nonlinear electro-thermal memory effect arising in a GaAs PHEMT. In particular is demonstrated the way with which the pure nonlinear electrical effect and the electro-thermal one combine and in turn determine a dispersive third-order intermodulation. The analysis is based on an accurate distributed model modified in order to take into account for the dynamic thermal behaviour under large signal operation. The results show a reduction of the intermodulation product in response to a reduction of the two tones frequency spacing, in agreement with the analytical treatment.