US3814993A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tuneable infrared photocathode
Assignee: United States Department of the Navy
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Filing: 1972-11-15
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Granted: 1974-06-04
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Expires: 1992-11-15
Abstract
Abstract A tuneable field assisted photocathode structured as a three layer double heterojunction device with a low work function cesium oxide coating on the electron emitting surface. An internal field assistance bias aids the flow of electrons from a narrow bandgap region, where they are photo-generated, to the wider bandgap negative electron affinity surface region for vacuum emission.
Inventors
- 👤 A Kennedy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 09:21
CPC Classifications
H; H01; H01J; H01J1/00; H01J1/02; H01J1/34; H01J2201/00; H01J2201/34; H01J2201/342; H01J2201/3421; H01J2201/3423
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
177 words
An epitaxially graded multijunction photoemitter responsive to radiation in the 1-2 micrometer spectral region comprising a three layer double heterojunction structure having an essentially constant lattice spacing throughout, wherein: a first layer of light absorbing III-V compound alloy semiconductor material having a narrow bandgap in the range of 0.65 - 0.8 eV functions as a detector of incident infrared radiation; a second layer of III-V compound alloy semiconductor material having a wide bandgap in the range of 1.65 - 1.75 eV is heteroepitaxially grown on the first layer and functions to block the hole current and aid the electron current when biased positively with respect to the detector layer; a third layer of III-V compound alloy semiconductor material having an intermediate Bandgap, with respect to layers one and two, epitaxially grown on the second layer for functioning as a high quantum efficiency electron emitter; first and second electrically conductive terminals attached respectively to the first and third layers of the heterojunction structure for effecting a positive biasing across the second layer with respect to the detector layer.
Claim 2
Dependent Claim
177 words
An epitaxially graded multijunction photoemitter responsive to radiation in the 1-2 micrometer spectral region comprising a three layer double heterojunction structure having an essentially constant lattice spacing throughout, wherein: a first layer of light absorbing III-V compound alloy semiconductor material having a narrow bandgap in the range of 0.65 - 0.8 eV functions as a detector of incident infrared radiation; a second layer of III-V compound alloy semiconductor material having a wide bandgap in the range of 1.65 - 1.75 eV is heteroepitaxially grown on the first layer and functions to block the hole current and aid the electron current when biased positively with respect to the detector layer; a third layer of III-V compound alloy semiconductor material having an intermediate Bandgap, with respect to layers one and two, epitaxially grown on the second layer for functioning as a high quantum efficiency electron emitter; first and second electrically conductive terminals attached respectively to the first and third layers of the heterojunction structure for effecting a positive biasing across the second layer with respect to the detector layer.
Claim 3
Dependent Claim
25 words
The epitaxially graded multijunction photoemitter of claim 1 wherein the three layers of III-V compound alloy semiconductor material consist of GaSbAs, AlSbAs and AlGaSbAs respectfully.
Claim 4
Dependent Claim
25 words
The epitaxially graded multijunction photoemitter of claim 1 wherein the three layers of III-V compound alloy semiconductor material consist of InAlAs, AlSbAs and AlInAsSb respectfully.
Claim 5
Dependent Claim
36 words
The photoemitter of claim 2 wherein the specific composition of the III-V quaternary compound alloys are determined in accordance with the alloy composition of Ga1 yAlyAs1 xSbx as read from the design curve of FIG. 2.
Claim 6
Dependent Claim
36 words
The photoemitter of claim 3 wherein the specific composition of the III-V quaternary compound alloys are determined in accordance with the alloy composition of In1 yAlyAs1 xSbx as read from the design curve of FIG. 4.
Claim 7
Dependent Claim
30 words
The photoemitter of claim 1 further including a layer of low work function material immediately absorbed on the exposed surface of the third layer of the electron emitting semiconductor material.
References Cited (Backward Citations)
US3408521A
Cited
US3667007A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-03 | 1977-12-03 | 1978-06-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-03 | 1981-12-03 | 1982-06-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-03 | 1985-12-03 | 1986-06-04 | $7700.00 | Window Closed / Lapsed |