Spectral sensitive solid-state photodetector

• US 9,482,578 B2
• Filed: 12/13/2011
• Issued: 11/01/2016
• Est. Priority Date: 12/14/2010
• Status: Expired due to Fees

• Current Assignee: Université d'Aix-Marseille
• Original Assignee: Aix-Marseille University
• Inventors: Gach, Jean-Luc
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): Riddick, Blake
• Application Number:
  US13/994,392
• Publication Number:
  US 20130335742A1
• Time in Patent Office: 1,785 Days
• Field of Search: 250/214.1, 250/208.1, 250/338.1, 257/438, 257/186
• US Class Current: 1/1
• CPC Class Codes: G01J 3/505 measuring the colour produced by lighting fixtures other than screens, monitors, displays or CRTs
• CPC Class Codes: H01L 27/14647 Multicolour imagers having a stacked pixel-element structure, e.g. npn, npnpn or MQW elements
• CPC Class Codes: H01L 31/02027 for devices working in avalanche mode
• CPC Class Codes: H01L 31/107 the potential barrier working in avalanche mode, e.g. avalanche photodiodes
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

A method for detecting photons includes subjecting a photodiode formed in a semi-conductive material, to a bias voltage such that an avalanche phenomenon can appear when a photon enters the photodiode in an avalanche layer extending into the semi-conductive material down to minimum and maximum depths so that it can be reached by photons having a wavelength between minimum and maximum wavelengths. The method also includes comparing the amplitude of a signal supplied by the photodiode with two threshold values, and deducing that the photodiode received a photon having a wavelength between two threshold wavelengths ranging between the minimum and maximum wavelengths, if the amplitude of the signal is between the two threshold values.

Claims

1. A method for detecting photons, comprising:

subjecting a semi-conductive material of a photodiode to a bias voltage such that an avalanche phenomenon is triggered in an avalanche layer of the semi-conductive material when a photon reaches the avalanche layer,

wherein the avalanche layer extends between minimum and maximum depths into the semi-conductive material from a surface thereof so that the avalanche layer can be reached by a photon having a wavelength ranging between minimum and maximum wavelengths,

the method further comprising;

generating, by the photodiode, a signal having an amplitude depending on a depth reached by a photon within the avalanche layer, the signal being generated with a gain that varies as a function of a wavelength of the photon received by the photodiode,

comparing, by a measuring circuit connected to the photodiode, the amplitude of the signal generated by the photodiode with two different threshold values, and

deducing, by the measuring circuit, that the photon received by the photodiode has a wavelength between two threshold wavelengths ranging between the minimum and maximum wavelengths, if the amplitude of the signal is between the two threshold values.

2. The method according to claim 1, further comprising counting, during an acquisition period, a number of pulses detected at terminals of the photodiode, having an amplitude between the two threshold values to obtain a value representative of a number of photons that have entered the photodiode during the acquisition period, and having a wavelength between the two threshold wavelengths.

3. The method according to claim 1, further comprising counting, during an acquisition period, a number of pulses detected at terminals of the photodiode, having an amplitude greater than the highest of the two threshold values to obtain a value representative of a number of photons that have entered the photodiode during the acquisition period, and having a wavelength below the lowest of the two threshold wavelengths.

4. The method according to claim 1, wherein the lowest of the two threshold values-corresponds to an extreme photon wavelength to be detected.

5. The method according to claim 1, further comprising:

comparing the amplitude of the signal supplied by the photodiode with several other threshold values, the two threshold values delimiting several ranges of amplitude values, and

counting during an acquisition period numbers of pulses of the signal in each of the ranges of amplitude values.

6. The method according to claim 5, wherein ranges of pulse amplitude values delimited by the threshold values are not contiguous and/or overlap.

7. The method according to claim 1, further comprising adjusting the threshold values to adjust ranges of wavelengths in which photons are to be detected.

8. The method according to claim 1, further comprising adjusting the bias voltage of the photodiode to change a thickness of the avalanche layer so that all the photons to be detected can reach the avalanche layer without going beyond the avalanche layer.

9. A device for detecting photons, comprising

a photodiode formed in a semi-conductive material,

a bias circuit connected to the photodiode and configured to subject the semi-conductive material to a bias voltage such that an avalanche phenomenon is triggered in an avalanche layer of the semi-conductive material when a photon reaches the avalanche layer, wherein the avalanche layer extends between minimum and maximum depths into the semi-conductive material from a surface thereof so that the avalanche layer can be reached by photons having a wavelength between minimum and maximum wavelengths, and wherein the photodiode generates a signal having an amplitude depending on a depth reached by a photon within the avalanche layer, the signal being generated with a gain that varies as a function of a wavelength of the photon received by the photodiode, and

a measurement circuit connected to the photodiode and configured to compare the amplitude of the signal generated by the photodiode with two different threshold values, and to deduce that the photon received by the photodiode has a wavelength between two threshold wavelengths ranging between the minimum and maximum wavelengths, if an amplitude of the signal is between the two threshold values.

10. The device according to claim 9, wherein the photodiode comprises a low-doped or undoped collection layer with a reduced thickness so that the avalanche layer can extend at least down to a depth reached by photons having an extreme wavelength to be detected.

11. The device according to claim 9, wherein the photodiode comprises a pn junction-made at a certain depth in the semi-conductive material, the semi-conductive material and the depth of the pn junction being chosen so that the semi-conductive material can be passed through by photons to be detected down to a depth likely to be located in the avalanche layer of the photodiode.

12. The device according to claim 9, wherein the measurement circuit is further configured to count, during an acquisition period, a number of pulses detected at terminals of the photodiode, having an amplitude between the two threshold values to obtain a value representative of a number of photons that have entered the photodiode during the acquisition period, and having a wavelength between the two threshold wavelengths.

13. The device according to claim 9, wherein the measurement circuit is further configured to count, during an acquisition period, a number of pulses detected at terminals of the photodiode, having an amplitude greater than the highest of the two threshold values to obtain a value representative of a number of photons that have entered the photodiode during the acquisition period, and having a wavelength below the lowest of the two threshold wavelengths.

14. The device according to claim 9, wherein the lowest of the two threshold values corresponds to an extreme photon wavelength to be detected.

15. The device according to claim 9, wherein the measurement circuit is further configured to:

compare the amplitude of the signal supplied by the photodiode with several other threshold values, the threshold values delimiting several ranges of amplitude values, and

count, during an acquisition period, numbers of pulses of the signal in each of the ranges of amplitude values.

16. The device according to claim 15, wherein ranges of pulse amplitude values delimited by the threshold values are not contiguous and/or overlap.

17. The device according to claim 9, further configured to adjust the threshold values to adjust ranges of wavelengths in which photons are to be detected.

18. The device according to claim 9, further configured to adjust the bias voltage of the photodiode so that all the photons to be detected can reach the avalanche layer without going beyond the avalanche layer.

19. An imager, comprising several detection devices, each comprising:

a photodiode formed in a semi-conductive material,

a bias circuit connected to the photodiode and configured to subject the semi-conductive material to a bias voltage such that an avalanche phenomenon is triggered in an avalanche layer of the semi-conductive material when a photon reaches the avalanche layer, wherein the avalanche layer extends between minimum and maximum depths into the semi-conductive material from a surface thereof so that the avalanche layer can be reached by photons having a wavelength between minimum and maximum wavelengths, and wherein the photodiode generates a signal having an amplitude depending on a depth reached by a photon within the avalanche layer, the signal being generated with a gain that varies as a function of a wavelength of the photon received by the photodiode, and

a measurement circuit connected to the photodiode and configured to compare the amplitude of the signal supplied by the photodiode with two different threshold values, and to deduce that the photon received by the photodiode has a wavelength between two threshold wavelengths ranging between the minimum and maximum wavelengths, if an amplitude of the signal is between the two threshold values,

wherein the photodiodes of the detection devices are disposed according to a matrix configuration.

20. The imager according to claim 19, wherein each photodiode comprises a low-doped or undoped collection layer with a reduced thickness so that the avalanche layer can extend at least down to a depth reached by photons having an extreme wavelength to be detected.

21. The imager according to claim 19, wherein each photodiode comprises a pn junction made at a certain depth in the semi-conductive material, the semi-conductive material and the depth of the pn junction being chosen so that the semi-conductive material can be passed through by photons to be detected down to a depth likely to be located in the avalanche layer of the photodiode.

22. The imager according to claim 19, wherein each measurement circuit is further configured to count, during an acquisition period, a number of pulses detected at terminals of the photodiode, having an amplitude between the two threshold values to obtain a value representative of a number of photons that have entered the photodiode during the acquisition period, and having a wavelength between the two threshold wavelengths.

23. The imager according to claim 19, wherein each measurement circuit is further configured to count, during an acquisition period, a number of pulses detected at terminals of the photodiode, having an amplitude greater than the highest of the two threshold values to obtain a value representative of a number of photons that have entered the photodiode during the acquisition period, and having a wavelength below the lowest of the two threshold wavelengths.

24. The imager according to claim 19, wherein the lowest of the two threshold values corresponds to an extreme photon wavelength to be detected.

25. The imager according to claim 19, wherein each measurement circuit is further configured to:

compare the amplitude of the signal supplied by the photodiode with several other threshold values, the threshold values delimiting several ranges of amplitude values, and

count during an acquisition period numbers of pulses of the signal in each of the ranges of amplitude values.

26. The imager according to claim 25, wherein ranges of pulse amplitude values delimited by the threshold values are not contiguous and/or overlap.

27. The imager according to claim 19, further configured to adjust the threshold values to adjust ranges of wavelengths in which photons are to be detected.

28. The imager according to claim 19, further configured to adjust the bias voltage of each photodiode so that all the photons to be detected can reach the avalanche layer of each photodiode without going beyond the avalanche layer.