Noise Sources in Semiconductor Detectors S W McKnight and C A DiMarzio
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
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
“Frictional” force Ensemble average: For time scales slow compared to thermal fluctuations:
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
Circuit Equation V R V
Fluctuation-Dissipation Theorem “Frictional” force is related to the time correlation of the rapidly varying random fluctuation force
Resistance and Noise Time-correlation of random thermal voltage fluctuations:
Spectral Density of Autocorrelation Function
Voltage and Current Thermal Fluctuations “Johnson” or “Nyquist” noise
Shot Noise or G-R Noise From Poisson statistics:
Noise in Photoconductors