US4115223A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Gallium arsenide photocathodes
Assignee: International Standard Electric Corp
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Filing: 1977-08-08
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Granted: 1978-09-19
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Expires: 1997-08-08
Abstract
Abstract This invention comprises methods and apparatus for bonding a transmission type III-V photocathode to a transparent substrate. An R.F. susceptor arrangement produces a marked temperature gradient for allowing the surface of the glass to conform to the shape of the semiconductor material without softening the bulk of the glass. The bonded assembly is then carefully annealed in an annealing furnace.
Inventors
- 👤 Edward John Thrush
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 07:32
CPC Classifications
C; C25; C25F; C25F3/00; C25F3/02; C25F3/14; H; H01; H01J; H01J9/00; H01J9/02; H01J9/12
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
180 words
A method of making a transmission type active layer, III-V semiconductor photocathode including the steps of: providing a semiconductive body containing a layer which is to form the active layer of the photocathode; preparing a billet of glass having a coefficient of expansion matched with said semiconductive body; placing a surface of the billet in contact with a surface of the semiconductive body to form an assembly of said billet and body; applying pressure between the body and the billet; heating the billet and body assembly by a susceptor arrangement of an induction heater to preferentially heat the semiconductive body to a temperature above the softening point of the glass while leaving the bulk of the billet at a temperature beneath said softening point; reducing the temperature of the assembly once the surface of the billet in contact with the semiconductive body has begun to flow; annealing the assembly at a reduced temperature; depositing an anti-reflection coating on an optical input face of said billet opposite said body; and removing a porton of said body to expose said active layer.
Claim 2
Independent Claim
180 words
A method of making a transmission type active layer, III-V semiconductor photocathode including the steps of: providing a semiconductive body containing a layer which is to form the active layer of the photocathode; preparing a billet of glass having a coefficient of expansion matched with said semiconductive body; placing a surface of the billet in contact with a surface of the semiconductive body to form an assembly of said billet and body; applying pressure between the body and the billet; heating the billet and body assembly by a susceptor arrangement of an induction heater to preferentially heat the semiconductive body to a temperature above the softening point of the glass while leaving the bulk of the billet at a temperature beneath said softening point; reducing the temperature of the assembly once the surface of the billet in contact with the semiconductive body has begun to flow; annealing the assembly at a reduced temperature; depositing an anti-reflection coating on an optical input face of said billet opposite said body; and removing a porton of said body to expose said active layer.
Claim 3
Dependent Claim
34 words
The method of claim 1 wherein the surface of the semiconductive body in contact with the billet is the surface of a recombination inhibition layer of a larger band gap over the active layer.
Claim 4
Dependent Claim
30 words
The method of claim 1 wherein the surface of the semiconductive body in contact with the billet is the surface of a glassy passivation layer directly covering the active layer.
Claim 5
Dependent Claim
18 words
The method of claim 2 wherein the surface of a glassy passivation layer covers the recombination inhibition layer.
Claim 6
Dependent Claim
23 words
The method of claim 1 wherein the billet and body assembly is induction heated under vacuum after having outgassed and annealed the billet.
Claim 7
Dependent Claim
19 words
The method of claim 1 wherein the billet and body assembly is induction heated in an atmosphere of argon.
Claim 8
Dependent Claim
33 words
The method of claim 1 wherein the billet and body assembly is induction heated in a susceptor arrangement consisting of a plate having a removable annulus fitted to one face of the plate.
Claim 9
Dependent Claim
21 words
The method of claim 7 wherein the body is housed in a recess in said one face of the susceptor plate.
Claim 10
Dependent Claim
24 words
The method of claim 8 wherein the billet is housed in the annulus and wherein said annulus is formed of at least two parts.
Claim 11
Dependent Claim
49 words
The method of claim 1 wherein the semiconductor body includes a p-type active layer epitaxially grown on an n-type blocking layer epitaxially grown on a p-type self-supporting substrate, and wherein a portion of the substrate is removed by electrochemical etching subsequent to annealing to expose the underlying blocking layer.
Claim 12
Dependent Claim
33 words
The method of claim 10 wherein electrochemical etchant is pumped through the tip of a tube which forms an electrochemical etching cathode to wash the etching waste products from the surface being etched.
Claim 13
Dependent Claim
45 words
The method of claim 10 wherein electrochemical etchant is pumped through a pipe in order to wash the etching waste products from the surface being etched, a wire coupled between the surface being etched and the outlet of said pipe forming the electrochemical etching cathode.
Claim 14
Dependent Claim
67 words
The method of claim 12 wherein the exposed portion of the n-type blocking layer is removed by a non-selective etch acting simultaneously with a subsidiary electrochemical etch, wherein the electrochemical etch current is modulated by illuminating the surface being etched with modulated light, and wherein the simultaneous etching is terminated when the active layer becomes exposed as determined by a reduction of the depth of current modulation.
Claim 15
Dependent Claim
59 words
The method of claim 1 wherein said semiconductive body includes a p-type active layer grown upon a semi-insulating self-supporting structure, and wherein the removing step includes removing at least part of the semi-insulating substrate by a cathodic inhibition selected etching process in which the p-type active layer is protected from attack by the etching by electrolytic current flow therethrough.
Claim 16
Dependent Claim
29 words
The method of claim 14 wherein terminal connection with the active layer for the cathodic inhibition selective etching is made via an electrode on the face of the billet.
Claim 17
Dependent Claim
55 words
The method of claim 14 wherein a selective etchant is used to a window through the substrate and the active layer to expose a portion of a GaAlAs layer epitaxially grown on the active layer, and wherein terminal contact is made with the GaAlAs layer through this window for the cathodic inhibition selective etching process.
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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) | 1981-09-18 | 1982-03-20 | 1982-09-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-09-18 | 1986-03-20 | 1986-09-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-09-18 | 1990-03-20 | 1990-09-19 | $7700.00 | Window Closed / Lapsed |