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

2. Sources of Noise Johnson Noise (Nyquist noise) Shot 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