US4476477A
Expired / Lapsed
US
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Graded bandgap multilayer avalanche photodetector with energy step backs
Assignee: Nokia Bell Labs
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Filing: 1982-02-23
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Granted: 1984-10-09
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Expires: 2002-02-23
Abstract
Abstract A multistage avalanche photodetector in which the ionization energy is provided by an energy band discontinuity is described. The photodetector provides low noise optical detection at low voltage.
Inventors
- 👤 Federico Capasso
- 👤 Won-Tien Tsang
- 👤 Gareth F. Williams
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 03:57
CPC Classifications
H; H10; H10F; H10F30/00; H10F30/20; H10F30/21; H10F30/22; H10F30/222; H10F30/225; H10F30/2255
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
72 words
An avalanche photodetector comprising a first layer having a first conductivity type, a second layer having a second conductivity type, and disposed intermediate said first layer and said second layer at least one compositionally varying layer having a composition varying from a low bandgap composition to a high bandgap composition, said compositionally varying layer having an energy band step back after said high bandgap that assists ionization of one type of carrier.
Claim 2
Dependent Claim
72 words
An avalanche photodetector comprising a first layer having a first conductivity type, a second layer having a second conductivity type, and disposed intermediate said first layer and said second layer at least one compositionally varying layer having a composition varying from a low bandgap composition to a high bandgap composition, said compositionally varying layer having an energy band step back after said high bandgap that assists ionization of one type of carrier.
Claim 3
Dependent Claim
20 words
A photodetector as recited in claim 1 in which said at least one compositionally varying layer is essentially continuously graded.
Claim 4
Dependent Claim
22 words
A photodetector as recited in claim 2 in which said at least one compositionally varying layer has an essentially linear compositional variation.
Claim 5
Dependent Claim
21 words
A photodetector as recited in claim 1 in which said at least one compositionally varying layer has at least three sub-layers.
Claim 6
Dependent Claim
41 words
A photodetector as recited in claim 1, 2, 3, or 4 in which said energy band step back is approximately equal to or greater than said one type of carrier ionization energy in the low gap material after said step back.
Claim 7
Dependent Claim
20 words
A photodetector as recited in claim 5 in which said energy band step back is primarily in the conduction band.
Claim 8
Dependent Claim
19 words
A photodetector as recited in claim 1, 2, 3, or 4 in which said step back is essentially abrupt.
Claim 9
Dependent Claim
36 words
A photodetector as recited in claim 7 in which said compositionally graded layer further comprises a slowly graded narrow gap region adjacent said energy band step back whereby the number of carriers that cause ionization increases.
Claim 10
Dependent Claim
38 words
A photodetector as recited in claim 7 in which said compositionally graded layer further comprises a slowly graded wide gap region adjacent said energy band step back whereby the average carrier energy above the band edge is increased.
Claim 11
Dependent Claim
18 words
A photodetector as recited in claim 1, 2, 3, or 4 in which said step back is graded.
Claim 12
Dependent Claim
36 words
A photodetector as recited in claim 10 in which said compositionally graded layer further comprises a slowly graded narrow gap region adjacent said energy band step back whereby the number of carriers that cause ionization increases.
Claim 13
Dependent Claim
38 words
A photodetector as recited in claim 10 in which said compositionally graded layer further comprises a slowly graded wide gap region adjacent said energy band step back whereby the average carrier energy above the band edge is increased.
Claim 14
Dependent Claim
59 words
A photodetector as recited in claim 1, 2, 3, or 4 in which said layers comprise at least one member selected from the group consisting of Al x Ga l-x As y Sb l-y /GaSb, In x Ga l-x Al y As l-y /InGaAs, In x Ga l-x As l-y Sb y /GaSb and Hg l-x Cd x Te.
Claim 15
Dependent Claim
21 words
A photodetector as recited in claim 1, 2, 3, or 4 further comprising a p-type dopant in said high bandgap composition.
Claim 16
Dependent Claim
21 words
A photodetector as recited in claim 1, 2, 3, or 4 further comprising a n-type dopant in said low bandgap composition.
Claim 17
Dependent Claim
21 words
A photodetector as recited in claim 1, 2, 3, or 4 further comprising a p-type dopant in said low bandgap composition.
Claim 18
Dependent Claim
21 words
A photodetector as recited in claim 1, 2, 3, or 4 further comprising a n-type dopant in said high bandgap composition.
Claim 19
Dependent Claim
20 words
A photodetector as recited in claim 5 in which said energy band step back is primarily in the valence band.
References Cited (Backward Citations)
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Cited
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US4213138A
Cited
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Cited
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Cited
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Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-10-09 | 1988-04-09 | 1988-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-10-09 | 1992-04-09 | 1992-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-10-09 | 1996-04-09 | 1996-10-09 | $7700.00 | Window Closed / Lapsed |