US5457331A
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Dual-band infrared radiation detector optimized for fabrication in compositionally graded HgCdTe
Assignee: OL Security LLC
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Filing: 1993-04-08
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Granted: 1995-10-10
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Expires: 2013-04-08
Abstract
Abstract A dual-band HgCdTe radiation detector (10) includes a four layer n-p + -p-n + structure, grown by LPE, upon a substrate (12). The four layers are, from a bottom layer next to the substrate to the surface: (a) a MWIR radiation responsive n-type absorbing layer (14); (b) a p + cap layer (16); (c) a LWIR radiation responsive p-type layer (18); and (d) an n+ top layer (20). The n + top layer has a compositional profile that is similar to the p-type cap layer. Operation of this structure involves biasing the top layer positive with respect to the bottom layer, which results in the collection of LWIR-generated electrons in the p-type layer. Biasing the top layer negative with respect to the bottom layer results in MWIR-generated holes being collected by the bottom n-p+ junction. In this mode, however, the detector structure rejects collection of LWIR-generated electrons because a compositional profile of the two p-type layers prevents the electrons from drifting to the bottom n-p+ junction and being collected.
Inventors
- 👤 Kenneth Kosai
- 👤 George R. Chapman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 13:35
CPC Classifications
H; H10; H10F; H10F39/00; H10F39/10; H10F39/12; H10F39/18; H10F39/184; H10F30/00; H10F30/20; H10F30/21; H10F30/22; H10F30/221; H10F30/2212; H10W; H10W90/00
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
285 words
A radiation detector structure responsive to electromagnetic radiation within two spectral bands, said radiation detector structure including a plurality of adjacently disposed layers of Group II-VI semiconductor material and comprising: a first layer comprised of Group II-VI semiconductor material, said first layer being doped to provide a first type of electrical conductivity and having a bandgap selected for absorbing radiation within a first spectral band; a second layer overlying said first layer, said second layer being comprised of Group II-VI semiconductor material, said second layer being doped to provide a second type of electrical conductivity that is opposite the first type of electrical conductivity said first and second layers forming a first junction; a third layer overlying said second layer, said third layer being comprised of Group II-VI semiconductor material, said third layer being doped to provide the second type of electrical conductivity and having a bandgap selected for absorbing radiation within a second spectral band; and a fourth layer overlying said third layer, said fourth layer being comprised of Group II-VI semiconductor material, said fourth layer being doped to provide the first type of electrical conductivity said third and fourth layers forming a second junction wherein said Group II-VI semiconductor material is comprised of Hg 1-x Cd x Te wherein x is varied through the thickness of the first layer in a direction toward the second layer so as to provide a decreasing bandgap energy within said first layer in the direction toward said second layer, and wherein x is varied through the thickness of the third layer in a direction toward the fourth layer so as to provide a decreasing bandgap energy within said third layer in the direction toward said fourth layer.
Claim 2
Dependent Claim
285 words
A radiation detector structure responsive to electromagnetic radiation within two spectral bands, said radiation detector structure including a plurality of adjacently disposed layers of Group II-VI semiconductor material and comprising: a first layer comprised of Group II-VI semiconductor material, said first layer being doped to provide a first type of electrical conductivity and having a bandgap selected for absorbing radiation within a first spectral band; a second layer overlying said first layer, said second layer being comprised of Group II-VI semiconductor material, said second layer being doped to provide a second type of electrical conductivity that is opposite the first type of electrical conductivity said first and second layers forming a first junction; a third layer overlying said second layer, said third layer being comprised of Group II-VI semiconductor material, said third layer being doped to provide the second type of electrical conductivity and having a bandgap selected for absorbing radiation within a second spectral band; and a fourth layer overlying said third layer, said fourth layer being comprised of Group II-VI semiconductor material, said fourth layer being doped to provide the first type of electrical conductivity said third and fourth layers forming a second junction wherein said Group II-VI semiconductor material is comprised of Hg 1-x Cd x Te wherein x is varied through the thickness of the first layer in a direction toward the second layer so as to provide a decreasing bandgap energy within said first layer in the direction toward said second layer, and wherein x is varied through the thickness of the third layer in a direction toward the fourth layer so as to provide a decreasing bandgap energy within said third layer in the direction toward said fourth layer.
Claim 3
Dependent Claim
38 words
A radiation detector structure as set forth in claim 1, and further comprising: a first electrical contact that is electrically coupled to said first layer; and a second electrical contact that is electrically coupled to said fourth layer.
Claim 4
Dependent Claim
31 words
A radiation detector structure as set forth in claim 2, and further comprising a third electrical contact that is electrically coupled to one of said third layer and said second layer.
Claim 5
Dependent Claim
29 words
A radiation detector structure as set forth in claim 1, wherein said first and second spectral bands are selected from the group consisting of SWIR, MWIR, LWIR and VLWIR.
Claim 6
Dependent Claim
89 words
A radiation detector structure as set forth in claim 1, wherein x is varied through the thickness of the second layer in a direction away from said first layer so as to provide an increasing bandgap energy within said second layer in the direction away from said first layer and wherein x is varied through the thickness of the fourth layer in a direction away from said third layer so as to provide an increasing bandgap energy within said fourth layer in the direction away from said third layer.
Claim 7
Dependent Claim
43 words
A radiation detector structure as set forth in claim 1, wherein said first layer is doped n-type, wherein said second layer is doped p + -type, wherein said third layer is doped p-type, and wherein said fourth layer is doped n + -type.
Claim 8
Dependent Claim
49 words
A radiation detector structure as set forth in claim 1, and further comprising a substrate having a first surface adjacent to a surface of said first layer, said substrate being selected from a material that is substantially transparent to electromagnetic radiation within said first and said second spectral bands.
Claim 9
Dependent Claim
47 words
A radiation detector structure as set forth in claim 7, and further comprising an antireflection coating that is disposed upon a second surface of said substrate, said second surface being opposite said first surface, said second surface being a radiation admitting surface of said radiation detector structure.
Claim 10
Dependent Claim
38 words
A radiation detector structure as in claim 2 further comprising a source of bias potential connected between said first and second electrical contacts capable of being switched to alternately reverse bias said first junction and said second junction.
Claim 11
Dependent Claim
51 words
A radiation detector structure as in claim 3 further comprising a source of bias potential connected to said third electrical contact on one side of said source and coupled to said first and second electrical contacts on a second side of said source to reverse bias said first and second junctions.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-10-09 | 1999-04-10 | 1999-10-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-10-09 | 2003-04-10 | 2003-10-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-10-09 | 2007-04-10 | 2007-10-10 | $7700.00 | Window Closed / Lapsed |