Optimization of pseudomorphic HEMT´s supported by numerical simulations

Measurements and simulations of three different pseudomorphic high electron mobility transistors (PHEMT´s) are presented. The PHEMT´s possess the same epitaxial structure but different geometrical properties. For the simulations, the generic device simulator MINIMOS-NT is employed. This simulator is not restricted to planar device surfaces but is able to model complex surface topologies including the effect of passivating dielectric layers. Mixed hydrodynamic and drift-diffusion simulations are demonstrated. They include the DC characteristics as well as the bias-dependent gate capacitances. Thus, bias-dependent current-gain cutoff frequencies f_T can be calculated. The results compare very well with the values obtained by small-signal parameter extractions from S-parameter measurements. Although a single consistent set of parameters is used for the simulations of all three devices, their characteristics are reproduced with an accuracy to our knowledge not reported before. Therefore, the DC and RF properties of PHEMT´s with geometries significantly different from the measured devices can be reliably predicted