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Photodiodes

Photodiodes. Photons incident on the depletion layer induce a current. In most cases, best response in the NIR. Response is linear over 6 – 7 orders of incident radiant power. Ingle and Crouch, Spectrochemical Analysis. Spectral Response of Photodiodes.

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Photodiodes

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  1. Photodiodes Photons incident on the depletion layer induce a current. In most cases, best response in the NIR. Response is linear over 6 – 7 orders of incident radiant power Ingle and Crouch, Spectrochemical Analysis

  2. Spectral Response of Photodiodes Shinya Inoue and Kenneth Spring, Video Microscopy, Plenum Press, New York, 1997.

  3. Avalanche Photodiode Hamamatsu Catalog http://micro.magnet.fsu.edu/primer/java/digitalimaging/avalanche/index.html

  4. Photodiode Arrays (PDA or DAD) Simultaneous  detection in a spectrophotometer. Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992.

  5. Charge Coupled Device (CCD) Ingle and Crouch, Spectrochemical Analysis www.piacton.com

  6. CCD Architecture SiO2 backing Pixel Array Image Area serial register amplifier http://micro.magnet.fsu.edu/primer/digitalimaging/concepts/ccdanatomy.html and Bryce Marquis (Haynes Lab)

  7. CCD Architecture “Channel Stops” form horizontal pixel boundaries Top View 3 electrodes form vertical pixel boundaries One pixel Electrode Insulating oxide n-type silicon p-type silicon Cross section Bryce Marquis (Haynes Lab)

  8. Charge Generation/Collection -V +V -V -V +V -V N-type P-type Incident photons excite electron-hole pairs, electrons gather in potential wells in each pixel

  9. CCD Rain Bucket Analogy • 1. Generation • 2. Collection • 3. Transfer • 4. Measurement Shinya Inoue and Kenneth Spring, Video Microscopy, Plenum Press, New York, 1997.

  10. Charge Generation/Collection -V +V -V -V +V -V N-type silica is doped with pentavalent species = excess electrons P-type is doped with trivalent species = excess holes N-type Potential Well P-type One Pixel

  11. 1 2 1 2 3 3 Charge Transfer +5V 0V -5V Every third electrode is coupled, charge packets are walked towards serial registry +5V 0V -5V +5V 0V -5V to serial registry Time-slice shown in diagram http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html

  12. 1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html

  13. 1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html

  14. 1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html

  15. 1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html

  16. 1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html

  17. 1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html

  18. Charge Transportation • Pixels at end of the array dump charge into serial register • Serial register walks charge packets to amplifier, where it is measured. amplifier

  19. Quantum Efficiency www.piacton.com

  20. Noise Sources in CCD • Shot Noise • Statistical variation of signal over time • Increases with the square of the intensity • Dark Signal Noise • Caused by thermal liberation of electrons • Strongly coupled to temperature • Readout Noise • Summation of noise associated with amplification of signal, and conversion from analogue to digital • Increases with the processing speed

  21. Other Issues: Bad Pixels Increasing hot pixels • Hot Pixels • Increased charge accumulation due to variations in chip surface. • Dead Pixels • Defective pixels that do not respond.

  22. Other Issues: Blooming

  23. Other Issues: Cosmic Rays Noise From Outer Space!!! * indicates cosmic rays

  24. Other Issues: Etaloning Etaloning www.piacton.com

  25. Other Features: Binning • On Chip Pixel Binning • Increases S/N • Shot noise decrease • Increased speed • Less storage space needed • Decreases resolution http://micro.magnet.fsu.edu/primer/digitalimaging/concepts/binning.html

  26. Are you getting the concept? List the advantages and disadvantages of using each of the discussed detectors to achieve single molecule detection.

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