US3972770A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of preparation of electron emissive materials
Assignee: International Telephone and Telegraph Corp
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Filing: 1975-03-21
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Granted: 1976-08-03
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Expires: 1995-03-21
Abstract
Abstract Preferential etches for Gallium Arsenide and Gallium Aluminum Arsenide materials provide a novel single crystalline layer thin film of GaAs for use as a free standing transmission secondary electron emitter or as a photocathode layer on an intermediate epitaxial layer of GaAlAs. Etching of a central area of a substrate layer of GaAs provides an annular rim supporting structure for the epitaxial GaAlAs and GaAs layers. A particular composition of hydrogen peroxide and ammonium hydroxide preferentially etches GaAs while hydrochloric acid preferentially etches GaAlAs.
Inventors
- 👤 William W. Stein
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 09:59
CPC Classifications
H; H01; H01J; H01J9/00; H01J9/02; H01J9/12; H01J1/00; H01J1/02; H01J1/32; H01J1/34; H10; H10P; H10P50/00; H10P50/60; H10P50/64; H10P50/642; H10P50/646; H01J2201/00; H01J2201/34; H01J2201/342; H01J2201/3421; H01J2201/3423
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
120 words
A method of making a radiation sensitive electron emissive semiconductor device comprising: forming a first relatively thin epitaxial layer of GaAlAs onto a relatively thick substrate layer of GaAs, said first layer being thinner than said substrate, forming a second thin monocrystalline epitaxial layer of GaAs onto said first epitaxial layer, said second layer being thinner than said first and substrate layers and sufficiently thin to be capable of emitting electrons within a vacuum upon excitation by radiation, and etching away a central portion of said substrate layer with an etchant which preferentially etches GaAs but does not etch GaAlAs to expose a surface of said GaAlAs layer and to leave a peripheral supporting rim of said GaAs substrate layer.
Claim 2
Independent Claim
120 words
A method of making a radiation sensitive electron emissive semiconductor device comprising: forming a first relatively thin epitaxial layer of GaAlAs onto a relatively thick substrate layer of GaAs, said first layer being thinner than said substrate, forming a second thin monocrystalline epitaxial layer of GaAs onto said first epitaxial layer, said second layer being thinner than said first and substrate layers and sufficiently thin to be capable of emitting electrons within a vacuum upon excitation by radiation, and etching away a central portion of said substrate layer with an etchant which preferentially etches GaAs but does not etch GaAlAs to expose a surface of said GaAlAs layer and to leave a peripheral supporting rim of said GaAs substrate layer.
Claim 3
Dependent Claim
21 words
The method of claim 1 wherein said etchant which preferentially etches GaAs is a solution of hydrogen peroxide and ammonium hydroxide.
Claim 4
Dependent Claim
27 words
The method of claim 2 wherein said GaAlAs is of the composition Ga x Al 1-x As where x is of a value from 0.7 to 0.
Claim 5
Dependent Claim
36 words
The method of claim 2 wherein said etchant is a mixture of equal volumes of a 30% solution of H 2 O 2 and a 28% solution of NH 4 OH, with a balance of water.
Claim 6
Dependent Claim
17 words
The method of claim 3 wherein said monocrystalline layer is from 3 to 8 microns in thickness.
Claim 7
Independent Claim
188 words
A method of making a radiation sensitive electron emissive conductor device comprising: forming a first relatively thin epitaxial layer of GaAlAs having the composition Ga x Al 1-x As, where x is of a value from 0.7 to 0 onto a relatively thick substrate layer of GaAs, said first layer being thinner than said substrate; forming a second thin monocrystalline epitaxial layer GaAs onto said first epitaxial layer; said second layer being thinner than said first and substrate layers and sufficiently thin to be capable of emitting electrons within a vacuum upon excitation of radiation; and etching away a central portion of said substrate layer with an etchant which is a solution of hydrogen peroxide and ammonium hydroxide and etching away a central portion of the first epitaxial layer with an etchant which preferentially etches GaAlAs but which does not etch GaAs to expose a surface of said second epitaxial layer providing a free standing layer of GaAs in said central area and to leave a peripheral supporting rim of said GaAs substrate layer aligned with said substrate rim to support said free standing layer at said rim.
Claim 8
Independent Claim
188 words
A method of making a radiation sensitive electron emissive conductor device comprising: forming a first relatively thin epitaxial layer of GaAlAs having the composition Ga x Al 1-x As, where x is of a value from 0.7 to 0 onto a relatively thick substrate layer of GaAs, said first layer being thinner than said substrate; forming a second thin monocrystalline epitaxial layer GaAs onto said first epitaxial layer; said second layer being thinner than said first and substrate layers and sufficiently thin to be capable of emitting electrons within a vacuum upon excitation of radiation; and etching away a central portion of said substrate layer with an etchant which is a solution of hydrogen peroxide and ammonium hydroxide and etching away a central portion of the first epitaxial layer with an etchant which preferentially etches GaAlAs but which does not etch GaAs to expose a surface of said second epitaxial layer providing a free standing layer of GaAs in said central area and to leave a peripheral supporting rim of said GaAs substrate layer aligned with said substrate rim to support said free standing layer at said rim.
Claim 9
Dependent Claim
25 words
The method of claim 6 including forming a third epitaxial layer of said GaAlAs on the side of said second epitaxial layer opposite said rim.
Claim 10
Dependent Claim
15 words
The method of claim 6 wherein said etchant which preferentially etches GaAlAs is hydrochloric acid.
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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) | 1979-08-03 | 1980-02-02 | 1980-08-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-03 | 1984-02-02 | 1984-08-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-03 | 1988-02-02 | 1988-08-03 | $7700.00 | Window Closed / Lapsed |