Analysis of RF noise performance of Si/SiGe pseudomorphic MOSFETs

A theoretical study of both buried and surface strained n-channel Si/SiGe MOSFETs is presented. The analysis focused on the possible benefits of the scaling on the AC and noise performance of the transistor for low-power applications using a 2D hydrodynamic model. The impedance field method was adopted to self-consistently obtain the current noise at the device´s terminals. The minimum noise figure (NF_min) dependence with the drain current was explained in terms of carrier transport in the channel. It was found that a pure reduction of the transistor´s gate length can be detrimental for subthreshold operation, but would lead to lower values of NF_min for medium and high current levels. Buried channel devices consistently showed higher values of the subthreshold slope and NF_min than the surface channel ones.