Noise investigation of SiGe and Si nMOSFETs with gate oxide grown by low temperature plasma anodisation

It is found that two noise components are responsible for the noise observed in the frequency range f=1 Hz to 100 kHz in SiGe and Si nMOSFETs with gate oxide grown by low temperature plasma anodisation. These components are the 1/f noise and the generation-recombination (GR) noise. It is shown that the 1/f noise component is due to fluctuations of the charge in slow oxide traps while the bulk centers located in some thin layer of the semiconductor give rise to the GR noise component. The analysis of the noise data allows one to get the following information concerning those oxide and bulk centers: (i) the density D_ot of the oxide traps in the SiGe nMOSFETs and the Si nMOSFETs are 7.2·10¹² cm^-2 (eV)^-1 and 1.4-10 ¹¹ cm^-2(eV).^-1, respectively, so that the value of D_ot is 50 times higher in SiGe devices than in Si devices; (ii) the density D_ot of the bulk GR centers is equal to 3·10¹⁰ cm^-2 in both the SiGe and Si devices; (iii) the electron and hole capture cross sections for these centers as well as their energy level and their depth below the oxide/semiconductor interface are also the same in the devices of both types. This suggests that those GR centers are of the same nature in all devices studied