Noise in Si/SiGe and Ge/SiGe MODFET

The progress of SiGe strained layer heteroepitaxy on virtual buffer substrates has opened up the opportunities for Si-based n- and p-channel HFETs with excellent RF performance. These devices have been reached outstanding high frequency figures of merit with f_MAX of 188 GHz and 135 GHz, for the n-HFET and the p-HFET, respectively. The Si/SiGe n-HFET exhibits a minimum noise figure NF_min of 0.3 dB with associated gain G_ass of 19 dB at 2.5 GHz, while for the Ge/SiGe p-HFET a NF_min of 0.5 dB with G_ass of 14 dB at 2.5 GHz have been reached. High frequency noise properties were simulated using Fospieszalski's and PRC - Van Der Ziel's noise models. Good agreement is obtained between experimental data and modelling owing to the investigation of the main contributions to n-HFET noise properties. Furthermore, coupled with experimental results at different gate length, hydrodynamic simulations with Silvaco software have been carried out to predict further RF and noise performance improvements when shrinking the gate length down to 70 nm. The low frequency noise of SiGe FETs is reported. All the preliminary result show that the noise level and corner frequency are in the same range as in III-V HEMTs.