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Noise Sources in Semiconductor Detectors

Noise Sources in Semiconductor Detectors. S W McKnight and C A DiMarzio. Sources of Noise. Johnson Noise (Nyquist noise) Random thermal fluctuations of electrons in resistive elements Shot Noise Statistical fluctuations in photo-electron generation Generation-Recombination Noise

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Noise Sources in Semiconductor Detectors

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  1. Noise Sources in Semiconductor Detectors S W McKnight and C A DiMarzio

  2. Sources of Noise • Johnson Noise (Nyquist noise) • Random thermal fluctuations of electrons in resistive elements • Shot Noise • Statistical fluctuations in photo-electron generation • Generation-Recombination Noise • Statistical fluctuations in current carrier generation due to photons and thermal excitation and recombinations • 1/f Noise • Low-frequency noise related to interfaces and contacts

  3. Johnson (Nyquist) Noise Connection between fluctuations and dissipation in system: Brownian motion: = slowly varying external force F(t) = random thermal force drives system back towards equilibrium (v=0 for =0) F’(t) = fluctuation force

  4. “Frictional” force Ensemble average: For time scales slow compared to thermal fluctuations:

  5. Electrical Analogy Circuit with self-inductance L: Current flows under influence of external emf + fluctuating thermal emf: V+ V(t) Average thermal force opposes current, drives system toward thermal equilibrium (I=0) Fluctuating thermal force creates thermal noise

  6. Circuit Equation V R V

  7. Fluctuation-Dissipation Theorem “Frictional” force is related to the time correlation of the rapidly varying random fluctuation force

  8. Resistance and Noise Time-correlation of random thermal voltage fluctuations:

  9. Spectral Density of Autocorrelation Function

  10. Voltage and Current Thermal Fluctuations “Johnson” or “Nyquist” noise

  11. Shot Noise or G-R Noise From Poisson statistics:

  12. Noise in Photoconductors

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