1. 1/f noise in devices
전광선

2. What is the 1/f noise?
A fluctuation in the conductance with a power spectral density proportional to

3. The cause of 1/f noise The conductance is
If conductance fluctuation is occurred which is fluctuated among the total carrier number or the mobility or both?
The reason is not revealed clearly.

4. Number Fluctuation Fluctuation of carrier number by traps.
In homogeneous bulk devices, Number fluctuation is not observed
In n-type MOST, Number fluctuation is observed because of the interface of bulk and oxide

5. Mobility Fluctuation Caused by scattering in the bulk region.
Depending on the phonon number fluctuation in bulk.
In MOST devices, mobility fluctuation is not fit to explain 1/f noise but p-type MOST devices.

6. Frequency up-conversion
Considered in oscillator and mixer.
Generation of phase noise of output signal to mix the current with impulse sensitivity function(ISF).
To consider power spectral density at the carrier frequency, the frequency range of 1/f noise is shifted upwardly.

7. Frequency up-conversion
Generation of phase noise
Frequency up-conversion of 1/f noise to carrier frequency

8. 1/f noise in GaAs HBT
At low forward current (<100uA), the 1/f noise density is determined by , by ( )
At high forward current (>100uA) the steep increase is due to the noise in the parasitic resistance.( )

9. 1/f noise in HBT
Can not observe a change in the current dependence of because of setting
guessed from

10. 1/f noise in GaAs HBT From the equation
If then the noise contribution from the base current is zero.
But there are no minimum point.→ can be neglected

11. 1/f noise in GaAs HBT
Sometimes a G-R noise contribution (leveling off of the spectral density) was observed at frequencies above 1kHz due to traps with a time constant lower than 0.1ms.
Comparing the 1/f noise of HBT with npn microwave silicon transistor, at the same current the 1/f noise ( )is much higher in HBT.In silicon npn transistor, 1/f base current noise is dominant and 1/f collector current noise is neglected.

12. 1/f noise in BJT
Mainly discussed in terms of mobility fluctuation(no oxide interface)
In small BJT, the internal base and emitter series resistance became more important than emitter and base current at high current.

13. 1/f noise in BJT
At low frequencies 1/f component is proportional to inverse frequency.
At high frequencies white component is independent to frequency.
Most of the spectra have corner frequencies in the range of 10Hz – 10kHz

14. 1/f noise in BJT Common collector configuration. At 1Hz
Both noise have a changeover of the current dependence at

15. 1/f noise in BJT
At low current ( <30uA) the 1/f noise can be strongly reduced by adjusting
and from
is dominant.
At high current ( >30uA) from
the internal resistance is more important than frequency in 1/f noise.

16. 1/f noise in MOSFET (n-type)
Mainly explained by carrier number fluctuation by tunneling of free charge into oxide trap close to the interface
Proportional to trap density.
Degradation by hot electron and ionizing irradiation as recent origin of number fluctuation

17. 1/f noise in MOSFET (p-type)
Generally thought by mobility fluctuation.
Because of larger distance from the interface, less noisy and independent to number fluctuation
Satisfying empirical relation
where alpha is constant

18. 1/f noise in MOSFET
Input noise is proportional to interface state density at fermi level and oxide trap density.
It explains that noise occurred by number fluctuation is affected to traps on oxide trap , oxide interface trap.

19. 1/f noise in MOSFET
1/f noise in n-type MOS is independent to gate bias.
It means that 1/f noise in n-type is independent to mobility fluctuation and affected by carrier number fluctuation.

20. 1/f noise in MOSFET
1/f noise in p-type MOS is dependent on the gate bias.
The gate bias dependence is explained by buried channel conduction.
It says 1/f noise in p-type MOS is explained by mobility fluctuation.

21. 1/f noise in MOSFET
P-type MOS suffers from mobility fluctuation generally but at high field condition, carrier fluctuation phenomenon is dominant.

22. Conclusion
1/f noise in electronic devices is explained by both number fluctuation and mobility fluctuation.
To reduce 1/f noise by number fluctuation, growing pure oxide(little trap) and new technique of surface etching are needed.
To reduce 1/f noise by mobility fluctuation, pure bulk is needed to make less scattering in bulk devices.

23. Reference
[1] Kleinpenning, “Location of Low-Frequency Noise Source in Submicron Bipolar Transistors”,IEEE on ED vol. 39 no
[2] Vandamme, Xiaosong Li,and D. Rigaud, “1/f noise in MOS Devices, Mobility or Number Fluctuation?”, IEEE on ED vol. 41, no. 11, 1994
[3] Kleinpenning and A.J.Holden, “1/f Noise in n-p-n GaAs/AlGaAs Heterojunction Bipolar Transistor: Impact of Intrinsic Transistor and Parasitic Series Resistances”, IEEE on ED vol. 40, no. 6, 1993
[4] Hooge, “1/f Noise Sources”, IEEE on ED vol. 41, no. 11, 1994
[5] Thomas H. Lee and A.Hajimiri, “Oscillator Phase Noise : A Tutorial”, IEEE on Solid State Circuits, vol. 35, no. 3, 2000
[6] Chang, Abidi and Viswanathan, “Flicker Noise in CMOS Transistor from Subthreshold to Strong Inversion at Various Temperature”, IEEE on ED vol. 41, no. 11, 1994
[7] Herman et al, “Correlation between 1/f noise and interference state density at the Fermi level in field effect transistor”, J. Appl. Phy., vol. 57, pp , 1985
Etc…..