A noise model for high electron mobility transistors

A model to explain the noise properties for AlGaAs/GaAs HEMT´s, AlGaAs/InGaAs/GaAs pseudomorphic HEMT´s (P-HEMT´s) and GaAs/AlGaAs inverted HEMT´s (I-HEMT´s) is presented. The model Is based on a self-consistent solution of Schrodinger and Poisson´s equations. The influence of the drain-source current, frequency and device parameters on the minimum noise figure F_min and minimum noise temperature T_min, for different HEMT structures are presented. The study shows that P-HEMT´s have a better noise performance than the normal and inverted HEMT´s. The present model predicts that a long gate P-HEMT device will exhibit a better noise performance than a conventional HEMT. There is a range of doped epilayer thickness where minimum noise figure is a minimum for pseudomorphic HEMT´s which is not observed in conventional and inverted HEMT´s. The calculated noise properties are compared with experimental data and the results show excellent agreement for all devices