Analytical current noise model based on nanoscale MOSFET.doc

1、1Analytical current noise model based on nanoscale MOSFETAbstract. In this paper， a physical understanding of excess noise component associated with transport mechanism in nanoscale MOSFET is developed. Based on the current flow image， current noise models valid for both uncorrelated and correlated

2、carrier injection are derived. The variation of suppression-factors with source-drain voltage， gate voltage， temperature and source-drain doping are investigated. The results we obtained with considering the combination of the two effects are consistent with those from experiments and the theoretica

3、lly explain is given. Key words： Nanoscale MOSFETs， Current Noise， Fano. While the drain thermal noise of long channel MOSFET agrees with the van der Ziel model1， considerably larger excess noise has been observed in MOSFET with channel lengths of deep sub-micron which severely hinder the applicatio

4、ns of RF CMOS. Since the channel length of MOSFET continues to downscaling， it becomes an urgent need to address the issue of noise reduction. A clear understanding and accurate prediction of 2this excess noise play an integral role in realization of optimal noise behavior. However， it is still an a

5、rgument about the component of excess noise. Many researchers have pointed out that short channel effects2-6 such as the hot electron effect， channel length modulation （CLM） ， carrier heating and velocity saturation （mobility degradation） would lead to excess noise. Together with experimental measur

6、ements， they developed all kinds of analytical thermal noise correctional models based on the above short channel effects. Although the thermal noise correctional models can well describe the noise characteristic for deep submicron MOSFET， they are not valid for nanoscale MOSFET7. Some researchers a

7、ttribute the failure of the thermal noise correctional models to the presence of shot noise8，9. Recent experiments， numerical simulations and theoretical results have proved the presence of shot noise in sub-100 nm MOSFET. Experimental data shows that for the device of L=20 nm ballisticity rate is 0

8、.3， the current noise is dominated by thermal noise， while for the device of L=10 nm BR is 0.5， and shot noise is dominated9. It is obviously that there is a link between the transport mechanism and noise mechanism. 3Thermal noise model can be used to describe the noise in long channel drift diffusi

9、ve MOSFET10 and shot noise model can predict the noise in ballistic MOSFET11. But for MOSFET whose transport mechanism is between drift diffusive and ballistic， i.e. quasi-ballistic MOSFET， there is still not an effective model to calculate the current noise8. In this paper， we analysis the componen

10、t of excess noise based on the current flow transport image and derive a noise model which is valid in nanoscale MOSFET. Fpoi is the fano factor without carrier interaction and Fsup is the one considering the effects of Fermi and coulomb. We can see from Fig .1， Fsup is much lower than Fpoi. Since t

11、he suppression is for shot noise， the more dominate the shot noise component， the more evident the suppression effect is. When L becomes shorter， temperature lower and Vds higher， the transport of carrier is dominated by ballistic. So the shot noise component is more than thermal noise component and

12、 the suppression cant be ignored. Higher Vgs induces more inelastic scattering events which make shot noise much lower that the Poisson value. Besides， the increased Vgs produces more inversion charge that lead to the increase of Fermi interaction of carriers that enhances the suppression. 4In this

13、paper， we build the current noise model of quasi-ballistic nanoscale MOSFET， considering Fermi effect and Coulomb interaction， this conclusion coincides with current results. The correctional model is more accuracy and can be used for noise suppression analysis. Acknowledgement This research was fin

14、ancially supported by Scientific Research Fund of Shaanxi Provincial Education Department（Grant No. 2013K1115） ，the National Natural Science Foundation of China （Grant No. 61106062） ，the Fundamental Research Funds for the Central Universities （Grant No. K50511050007） ，and the Fundamental Research Fu

15、nds for AnKang University （Grant No. AYQDZR201206） References 1 A.Van der Ziel， and E.R. Chenette， Noise in Solid State Devices， Advances in Electronics and Electron Physics， vol.46， pp. 313-383， 1978. 2 Klein P， An analytical thermal noise model of deep submicron MOSFETs， Electron Device Letters， v

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