Two-color barrier photodetector with dilute-nitride active region

Patent metadata

Field	Value
Publication number	US-9698192-B1
Application number	US-201514825597-A
Country	US
Kind code	B1
Filing date	Aug 13, 2015
Priority date	Aug 13, 2014
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

Embodiments described herein relate to a dual-band photodetector. The dual-band photodetector includes a barrier layer ( 10 ) disposed between two infrared absorption layers ( 8, 12 ) wherein the barrier layer ( 10 ) is lattice matched to at least one of the infrared absorption layers ( 8, 12 ). Furthermore, one infrared absorption layer includes dilute nitride to adjust the band gap to a desired cut-off wavelength while maintaining valence-band alignment with the barrier layer. Embodiments also relate to a system and processes for producing the photodetector fabricated from semiconductor materials.

First claim

We claim:

1. A photodetector, comprising:
a first absorption layer of a bulk alloy having a predetermined doping type to absorb photons in a first infrared (IR) wavelength band of a first wavelength range;
a second absorption layer comprising a dilute nitride alloy having a predetermined doping type to absorb photons in a second IR wavelength band of a second wavelength range; and
a barrier layer disposed between the first absorption layer and the second absorption layer,
wherein:
the first and second IR wavelength bands are spectrally separated with the first wavelength range being lower than the second wavelength range;
the barrier layer and the second absorption layer have valence band energy aligned with the first absorption layer, and
at least one of the barrier layer and the second absorption layer is lattice matched to the first absorption layer.

2. The photodetector of claim 1 , wherein:
the first range of wavelengths includes a first portion in a long-wavelength IR (LWIR) band; and
the second range of the wavelengths includes a second portion of the long-wavelength IR (LWIR) band wherein the first portion and the second portion are different.

3. The photodetector of claim 1 , further comprising:
a substrate disposed on an optical window side of the first absorption layer, such that the first absorption layer is lattice matched to the substrate.

4. The photodetector of claim 1 , further comprising
a buffer layer disposed between the first absorption layer and the substrate.

5. The photodetector of claim 1 , further comprising a substrate and a buffer layer disposed between the first absorption layer and the substrate, such that the second absorption layer, the barrier layer, and the first absorption layer are lattice matched to the buffer layer.

6. The photodetector of claim 1 , wherein the second absorption layer is subdivided into a plurality of contact regions to delineate pixels, each contact region having an active area and a passivated area; and
further comprising a ground coupled to the first absorption layer.

7. The photodetector of claim 6 , wherein:
the first absorption layer has a chemical potential therein such that, when a reverse bias is applied to the photodetector via the plurality of contact regions and the ground, minority carriers from the first absorption layer are driven across the barrier layer such that the photodetector is responsive to photons in a spectral band of the first absorption layer; and
the second absorption layer has a chemical potential therein such that, when a forward bias is applied to the photodetector via the plurality of contact regions and the ground, minority carriers from the second absorption layer are driven across the barrier layer such that the photodetector is responsive to photons in a spectral band of the second absorption layer.

8. The photodetector of claim 1 , wherein:
the first IR wavelength band comprises a medium-wavelength IR (MWIR) range; and
the second IR wavelength band comprises a long-wavelength IR (LWIR) range.

9. The photodetector of claim 8 , wherein:
the first absorption layer comprises a MWIR absorption layer comprising an InAsSb alloy;
the barrier layer comprises an AlGaAsSb alloy; and
the second absorption layer comprises a LWIR absorption layer comprising an InNAsSb alloy wherein In is indium; As is arsenic; Sb is antimony; Al is aluminum, N is nitrogen and Ga is gallium.

10. A system, comprising:
a readout integrated circuit (ROIC); and
a dual-band photodetector configured to collect photons in a first infrared (IR) wavelength band when a first bias is applied to the photodetector and collect photons in a second infrared (IR) wavelength band when a second bias is applied to the photodetector, the photodetector, comprising:
a first absorption layer of a bulk alloy having a predetermined doping type to absorb photons in a first infrared (IR) wavelength band of a first wavelength range;
a second absorption layer comprising a dilute nitride alloy having a predetermined doping type to absorb photons in a second IR wavelength band of a second wavelength range; and
a barrier layer disposed between the first absorption layer and the second absorption layer,

wherein:
the first and second IR wavelength bands are spectrally separated with the first wavelength range being lower than the second wavelength range;
the barrier layer and the second absorption layer have valence band energy aligned with the first absorption layer; and
at least one of the barrier layer and the second absorption layer is lattice matched to the first absorption layer.

11. The system of claim 10 , wherein:
the first range of wavelengths includes a first portion in a long-wavelength IR (LWIR) band; and
the second range of the wavelengths includes a second portion of the long-wavelength IR (LWIR) band wherein the first portion and the second portion are different.

12. The system of claim 10 , further comprising:
a substrate disposed on an optical window side of the first absorption layer, such that the first absorption layer is lattice matched to the substrate.

13. The system of claim 10 , further comprising a substrate and a buffer layer disposed between the first absorption layer and the substrate, such that the second absorption layer, the barrier layer, and the first absorption layer are lattice matched to the buffer layer.

14. A system of claim 10 , wherein the second absorption layer is subdivided into a plurality of contact regions to delineate pixels, each contact region having an active area and a passivated area; and
further comprising a ground coupled to the first absorption layer.

15. The system of claim 14 , wherein:
the first bias is a reverse bias and the second bias is a forward bias;
the first absorption layer has a chemical potential therein such that, when the reverse bias is applied to the photodetector via the plurality of contact regions and the ground, minority carriers from the first absorption layer are driven across the barrier layer such that the photodetector is responsive to photons in a spectral band of the first absorption layer; and
the second absorption layer has a chemical potential therein such that, when the forward bias is applied to the photodetector via the plurality of contact regions and the ground, minority carriers from the second absorption layer are driven across the barrier layer such that the photodetector is responsive to photons in a spectral band of the second absorption layer.

16. The system of claim 10 , wherein:
the first IR wavelength band comprises a medium-wavelength IR (MWIR) range; and
the second IR wavelength band comprises a long-wavelength IR (LWIR) range.

17. The system of claim 16 , wherein:
the first absorption layer comprises a MWIR absorption layer comprising an InAsSb alloy;
the barrier layer comprises an AlGaAsSb alloy; and
the second absorption layer comprises a LWIR absorption layer comprising an InNAsSb alloy wherein In is indium; As is arsenic; Sb is antimony; Al is aluminum, N is nitrogen and Ga is gallium.

18. A method, comprising:
forming, for a photodetector, a first absorption layer of a bulk alloy having a predetermined doping type to absorb photons in a first infrared (IR) wavelength band of a first wavelength range;
forming, for the photodetector, a second absorption layer comprising a dilute nitride alloy having a predetermined doping type to absorb photons in a second IR wavelength band of a second wavelength range; and
forming, for the photodetector, a barrier lay

Assignees

• Lockheed Corp

Inventors

• Crook Adam M
• Reason Matthew J
• Spells Barrett

Classifications

• H01L31/03044

  Electricity · mapped topic

• H01L27/14652 Primary

  Electricity · mapped topic

• H01L31/1856

  Electricity · mapped topic

• H01L31/109

  Electricity · mapped topic

• H01L27/14683

  Electricity · mapped topic