OPTIMIZATION OF PSEUDOMORPHIC HEMTS SUPPORTED BY NUMERICAL SIMULATIONS

Measurements and simulations of three different pseudomorphic high ele ctron mobility transistors (PHEMT's) are presented. The PHEMT's posses s the same epitaxial structure but different geometrical properties. F or the simulations, the generic device simulator MINIMOS-NT is employe d. This simulator is not restricted to planar device surfaces but is a ble to model complex surface topologies including the effect of passiv ating dielectric layers. Mixed hydrodynamic and drift-diffusion simula tions are demonstrated. They include the DC characteristics as well as the bias-dependent gate capacitances. Thus, bias-dependent current-ga in cutoff frequencies f(T) can be calculated. The results compare very well with the values obtained by small-signal parameter extractions f rom S-parameter measurements, Although a single consistent set of para meters is used for the simulations of all three devices, their charact eristics are reproduced with an accuracy to our knowledge not reported before. Therefore, the DC and RF properties of PHEMT's with geometrie s significantly different from the measured devices can be reliably pr edicted.