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

Abstract

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/sub ot/ of the oxide traps in the SiGe nMOSFETs and the Si nMOSFETs are 7.2/spl middot/10/sup 12/ cm/sup -2/ (eV)/sup -1/ and 1.4-10/sup 11/ cm/sup -2/(eV)./sup -1/, respectively, so that the value of D/sub ot/ is 50 times higher in SiGe devices than in Si devices; (ii) the density D/sub ot/ of the bulk GR centers is equal to 3/spl middot/10/sup 10/ cm/sup -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.