Abstract

The paper describes an analytical, CAD-oriented quasi-2D noise model for AlGaAs-GaAs HEMTs. The model is based on an improved version of the Ando and Itoh approach [2], in which the sheet density of the two-dimensional electron gas (2DEG) as a function of the gate bias is described by a numerical charge control model allowing for deep and shallow donors in the AlGaAs supply layer. The Ando and Itoh's power-law analytical gate control model is then fitted to the numerical charge control model; this yields accurate results in the low-noise operating region of HEMT's. Improved output conductance and low-field mobility models have been implemented to achieve a better agreement with experimental DC data. A critical discussion is presented on the effect of microscopic parameters like the effective thickness of the 2DEG, on the overall noise prediction of the model. Finally, comparisons are presented between the AC and noise model predictions and measurements carried out on a standard 0.5 mm SIEMENS HEMT.