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Single-Photon Avalanche Diodes (SPADs) Demystified

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A short presentation I created during my graduate studies to explain how SPADs work and how to use them

Published in: Engineering
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Single-Photon Avalanche Diodes (SPADs) Demystified

  1. 1. 1FABRIZIO GUERRIERI SPAD DEMYSTIFIED SINGLE-PHOTON AVALANCHE DIODE DEMYSTIFIED Fabrizio Guerrieri
  2. 2. 2FABRIZIO GUERRIERI SPAD DEMYSTIFIED LET’S CONSIDER THE TYPICAL PN JUNCTION I-V CHARACTERISTICS…
  3. 3. 3FABRIZIO GUERRIERI SPAD DEMYSTIFIED AVALANCHE CURRENT (JUNCTION BREAKDOWN) DIRECT CURRENT INVERSE CURRENT DUE TO THERMAL GENERATION IN THE DEPLETED ZONE PN JUNCTION
  4. 4. 4FABRIZIO GUERRIERI SPAD DEMYSTIFIED AVALANCHE CURRENT (JUNCTION BREAKDOWN) DIRECT CURRENT INVERSE CURRENT DUE TO THERMAL GENERATION IN THE DEPLETED ZONE PN JUNCTION THE SPAD WORKS HERE
  5. 5. 5FABRIZIO GUERRIERI SPAD DEMYSTIFIED HOW DOES A SPAD WORK?
  6. 6. 6FABRIZIO GUERRIERI SPAD DEMYSTIFIED WITH A REVERSE VOLTAGE BELOW BREAKDOWN NO CURRENT FLOWS
  7. 7. 7FABRIZIO GUERRIERI SPAD DEMYSTIFIED
  8. 8. 8FABRIZIO GUERRIERI SPAD DEMYSTIFIED AT THE BEGINNING, NO CURRENT FLOWS EVEN WITH A REVERSE VOLTAGE ABOVE BREAKDOWN
  9. 9. 9FABRIZIO GUERRIERI SPAD DEMYSTIFIED
  10. 10. 10FABRIZIO GUERRIERI SPAD DEMYSTIFIED AN AVALANCHE CURRENT IS TRIGGERED BY THE FIRST PHOTON GENERATING AN ELECTRON/HOLE PAIR IN THE DEPLETED REGION
  11. 11. 11FABRIZIO GUERRIERI SPAD DEMYSTIFIED
  12. 12. 12FABRIZIO GUERRIERI SPAD DEMYSTIFIED THE BRANCHED CHARACTERISTIC OF A SPAD
  13. 13. 13FABRIZIO GUERRIERI SPAD DEMYSTIFIED OBVIOUSLY A FRONT-END CIRCUIT (WE CALL IT QUENCHING CIRCUIT) IS NEEDED IN ORDER TO: 1. ENABLE THE SPAD RISING THE REVERSE VOLTAGE ABOVE BREAKDOWN 2. DETECT THE AVALANCHE CURRENT 3. QUENCH THE AVALANCHE CURRENT LOWERING THE REVERSE VOLTAGE BELOW BREAKDOWN
  14. 14. 14FABRIZIO GUERRIERI SPAD DEMYSTIFIED TWO MAIN ADVANTAGES 1. SINGLE-PHOTON LEVEL SENSITIVITY 2. ELECTRONIC PULSE’S RISING EDGE WITH VERY LOW TIME JITTER (30 ps OR BETTER) HOW CAN I USE A SPAD?
  15. 15. 15FABRIZIO GUERRIERI SPAD DEMYSTIFIED 1. TIME CORRELATED SINGLE-PHOTON COUNTING (TCSPC) (WE INFORMALLY CALL IT “PHOTON TIMING”) 2. TIME OF FLIGHT (TOF) 3. PHOTON-COUNTING HOW CAN I USE A SPAD?
  16. 16. 16FABRIZIO GUERRIERI SPAD DEMYSTIFIED 1 - PHOTON TIMING
  17. 17. 17FABRIZIO GUERRIERI SPAD DEMYSTIFIED 1 - PHOTON TIMING
  18. 18. 18FABRIZIO GUERRIERI SPAD DEMYSTIFIED After some laser pulses… 1 - PHOTON TIMING
  19. 19. 19FABRIZIO GUERRIERI SPAD DEMYSTIFIED After some laser pulses… After more laser pulses… 1 - PHOTON TIMING
  20. 20. 20FABRIZIO GUERRIERI SPAD DEMYSTIFIED After some laser pulses… After more laser pulses… 1 - PHOTON TIMING
  21. 21. 21FABRIZIO GUERRIERI SPAD DEMYSTIFIED After some laser pulses… After more laser pulses… After MANY laser pulses… 1 - PHOTON TIMING
  22. 22. 22FABRIZIO GUERRIERI SPAD DEMYSTIFIED 2 – TIME-OF-FLIGHT
  23. 23. 23FABRIZIO GUERRIERI SPAD DEMYSTIFIED 2 – TIME-OF-FLIGHT
  24. 24. 24FABRIZIO GUERRIERI SPAD DEMYSTIFIED 2 – TIME-OF-FLIGHT
  25. 25. 25FABRIZIO GUERRIERI SPAD DEMYSTIFIED Laser pulse’s shape Estimated TOF 2 – TIME-OF-FLIGHT
  26. 26. 26FABRIZIO GUERRIERI SPAD DEMYSTIFIED 3 - PHOTON COUNTING THE QUENCHING CIRCUIT DELIVERS AN OUTPUT PULSE EVERYTIME THE SPAD DETECTS A PHOTON
  27. 27. 27FABRIZIO GUERRIERI SPAD DEMYSTIFIED 3 - PHOTON COUNTING IN OUR ARRAYS EVERY PIXEL CONTAINS EVERYTHING TO DO PHOTON-COUNTING
  28. 28. 28FABRIZIO GUERRIERI SPAD DEMYSTIFIED #photons
  29. 29. 29FABRIZIO GUERRIERI SPAD DEMYSTIFIED #photons FRAME START
  30. 30. 30FABRIZIO GUERRIERI SPAD DEMYSTIFIED #photons
  31. 31. 31FABRIZIO GUERRIERI SPAD DEMYSTIFIED #photons
  32. 32. 32FABRIZIO GUERRIERI SPAD DEMYSTIFIED #photons
  33. 33. 33FABRIZIO GUERRIERI SPAD DEMYSTIFIED #photons FRAME START FRAME STOP

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