Room temperature, low-light-level visible imager

• US 6,476,374 B1
• Filed: 04/25/2000
• Issued: 11/05/2002
• Est. Priority Date: 04/25/2000
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Innovative Technology Licensing LLC
• Inventors: Dewames, Roger E., McDermott, Brian T., Sullivan, Gerard J., Kozlowski, Lester J.
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): Song, Hoon K.
• Application Number:
  US09/557,133
• Time in Patent Office: 924 Days
• Field of Search: 250/214.1, 257/615, 257/82, 257/114, 257/444, 257/446, 257/448, 257/459, 257/461
• US Class Current: 250/214.1
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14634 Assemblies, i.e. Hybrid structures
• CPC Class Codes: H01L 31/101 Devices sensitive to infrared, visible or ultraviolet radiation
• CPC Class Codes: H01L 31/1035 the devices comprising active layers formed only by AIIIBV compounds

Abstract

A photodetector sensitive to visible and shorter wavelengths is capable of single photon sensitivity at room temperatures and video frame rates. It includes (a) a compound semiconductor photodiode, biased below its avalanche breakdown threshold, comprising III-V elemental components and having a bandgap with transition energy higher than the energy of infrared photons; and (b) a high trans-impedance interface circuit, arranged to receive a signal from the photodiode junction and to amplify said signal. Preferably, the photodiode junction is integrated in a first microstructure on a first substrate, and its interface circuit in a second microstructure on a second substrate. Both microstructures are then joined in a laminar, sandwich-like structure and communicate via electrically conducting contacts.

Claims

1. A high-sensitivity photodetector for detecting radiation in the visible or shorter wavelength regions of the spectrum, suitable for room-temperature operation, comprising:

a compound semiconductor photodiode which generates a detector current in response to incident photons, said photodiode biased below its avalanche breakdown threshold, comprising III-V elemental components and having a bandgap with transition energy higher than the energy of infrared photons;

a high trans-impedance interface circuit, arranged to receive a signal from said photodiode junction and amplify said signal, wherein said photodiode junction is integrated on a first substrate and said interface circuit is on a second substrate.

2. The photodetector of claim 1, wherein said photodiode junction is integrated in a first microstructure on said first substrate, said interface circuit is in a second microstructure on said second substrate, and said first and second microstructures are joined in a laminar fashion,

and wherein said first and second microstructures communicate via electrically conducting contacts.

3. The photodetector of claim 2, wherein electrically conducting contacts comprise indium.

4. The photodetector of claim 3, wherein said interface circuit comprises:

a load FET, having a source arranged to receive a small signal from said photodiode; and

an amplifier that is connected in a negative feedback loop around said load FET'"'"'s gate-to-source voltage.

5. The photodetector of claim 4, wherein said interface circuit further comprises:

a sampling circuit that samples the output of said amplifier, said sampling circuit comprising;

a capacitor that integrates the amplifier output;

an access switch which is clocked at a sampling frequency to read said output; and

a reset switch to discharge said capacitor after said voltage is read.

6. The photodetector of claim 1, wherein said bandgap is at least 1.77 electron volts.

7. The photodetector of claim 1, wherein said bandgap is at least 1.98 electron volts.

8. The photodetector of claim 1, wherein said bandgap is at least 2.07 electron volts.

9. The photodetector of claim 1, wherein said bandgap is at least 2.25 electron volts.

10. The photodetector of claim 1, wherein said photodiode comprises:

a detector layer comprising aluminum gallium arsenide; and

a substrate layer comprising gallium arsenide.

11. The photodetector of claim 1, wherein said photodiode comprises:

a detector layer comprising aluminum indium gallium arsenide, and a substrate layer comprising indium phosphide.

12. The photodetector of claim 1, wherein said photodiode comprises:

a detector layer comprising gallium phosphide; and

a substrate layer comprising indium phosphide.

13. The photodetector of claim 1, wherein said photodiode comprises:

a detector layer comprising indium gallium nitride; and

a substrate layer comprising sapphire.

14. An imaging array for use at room temperatures to detect images from low-level visible, ultraviolet or shorter illumination, suitable for use at video frame rates, comprising:

a plurality of addressable photodetecting cells, each said cell comprising;

a compound semiconductor photodiode which generates a detector current in response to incident photons, said photodiode biased below its avalanche breakdown threshold, comprising III-V elemental components and having a bandgap with transition energy higher than the energy of infrared photons;

a high trans-impedance interface circuit, arranged to receive a signal from said photodiode junction and amplify said signal,

wherein said photodiode is integrated on a first substrate and said interface circuit is on a second substrate.

15. The imaging array of claim 14, wherein said photodiode is integrated in a first microstructure on said first substrate, said interface circuit is in a second microstructure on said second substrate, and said first and second microstructures are joined in a laminar fashion,

and wherein said first and second microstructures communicate via electrically conducting contacts.

16. The imaging array of claim 14, wherein said electrically conducting contacts comprise indium.

17. The imaging array of claim 14, wherein said interface circuit comprises:

a load FET, having a source arranged to receive a small signal from said photodiode; and

an amplifier that is connected in a negative feedback loop around said load FET'"'"'s gate-to-source voltage.

18. The imaging array of claim 14, wherein said interface circuit further comprises:

a sampling circuit that samples the output of said amplifier, said sampling circuit comprising;

a capacitor that integrates the amplifier output;

an access switch which is clocked at a sampling frequency to read said output; and

a reset switch that is clocked at said sampling frequency to discharge said capacitor after said voltage is read.

19. The imaging array of claim 14, wherein said bandgap is at least 1.77 electron volts.

20. The imaging array of claim 14, wherein said bandgap is at least 1.98 electron volts.

21. The imaging array of claim 14, wherein said bandgap is at least 2.07 electron volts.

22. The imaging array of claim 14, wherein said bandgap is at least 2.25 electron volts.

23. The imaging array of claim 14, wherein said photodiode comprises:

a detector layer comprising aluminum gallium arsenide; and

a substrate layer comprising gallium arsenide.

24. The imaging array of claim 14, wherein said photodiode comprises:

a detector layer comprising aluminum indium gallium arsenide, and

a substrate layer comprising indium phosphide.

25. The imaging array of claim 14, wherein said photodiode comprises:

a detector layer comprising gallium phosphide; and

a substrate layer comprising indium phosphide.

26. The imaging array of claim 14, wherein said photodiode comprises:

a detector layer comprising indium gallium nitride; and

a substrate layer comprising sapphire.

27. The imaging array of claim 14, wherein the respective interface circuits of said cells have variable gain.

28. The imaging array of claim 27, wherein the gain of said respective interface circuits is variably set in a manner complementary to a non-uniformity in a response of respective photodiodes of said cells.