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-consisten t solution of Schrodinger and Poisson's equations. The influence of th e drain-source current, frequency and device parameters on the minimum noise figure F(min) and minimum noise temperature T(min) for differen t HEMT structures are presented. The study shows that P-HEMT's have a better noise performance than the normal and inverted HEMT's. The pres ent model predicts that a long gate I-HEMT device will exhibit a bette r noise performance than a conventional HEMT. There is a range of dope d epilayer thickness where minimum noise figure is a minimum for pseud omorphic HEMT's which is not observed in conventional and inverted HEM T's. The calculated noise properties are compared with experimental da ta and the results show excellent agreement for all devices.