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US5262633A
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Wideband anti-reflection coating for indium antimonide photodetector device and method of forming the same
Assignee: Raytheon Co
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Filing: 1992-08-21
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Granted: 1993-11-16
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Expires: 2012-08-21
Abstract
Abstract A four-layer, wideband anti-reflection coating (30) is formed on a light-receiving surface (22) of an indium antimonide (InSb) photodetector (10) to enable detection of light at visible as well as infrared wavelengths. The layers (30a,30b,30c,30d) each have an optical thickness of approximately one-quarter wavelength at a reference wavelength of 1.6 microns. The refractive indices of the layers (30a,30b,30c,30d) are stepped down from the surface (22), having values of approximately 3.2/2.6/1.9/1.45 respectively. The second layer (30b) is preferably formed of silicon suboxide (SiO 0<X<1 ) by electron-beam deposition of silicon in an oxygen backfill to obtain a refractive index between the indices of silicon and silicon monoxide. A thin passivation layer (26) of germanium or silicon nitride is formed on the surface (22) under the anti-reflection coating (30) to inhibit a flashing effect at infrared wavelengths after exposing to the ultraviolet (UV) and/or visible light.
Inventors
- 👤 Ichiro Kasai
- 👤 Herbert L. Hettich
- 👤 Stephen L. Lawrence
- 👤 James E. Randolph
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:43
CPC Classifications
G; G02; G02B; G02B1/00; G02B1/10; G02B1/11; G02B1/113; G02B1/115
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
148 words
An anti-reflection coating for a light-receiving surface of a photodetector device, comprising: a first substantially transparent layer which is formed over said surface and has an optical thickness of approximately λ 0 /4, where λ 0 is a predetermined reference wavelength, and an index of refraction between approximately 3.2 and 3.3; a second substantially transparent layer which is formed over the first layer and has an optical thickness of approximately λ 0 /4, and an index of refraction between approximately 2.6 and 2.7; a third substantially transparent layer which is formed over the second layer and has an optical thickness of approximately λ 0 /4 and an index of refraction between approximately 1.9 and 2.0; and a fourth substantially transparent layer which is formed over the third layer and has an optical thickness of approximately λ 0 /4 and an index of refraction between approximately 1.4 and 1.5.
Claim 2
Dependent Claim
148 words
An anti-reflection coating for a light-receiving surface of a photodetector device, comprising: a first substantially transparent layer which is formed over said surface and has an optical thickness of approximately λ 0 /4, where λ 0 is a predetermined reference wavelength, and an index of refraction between approximately 3.2 and 3.3; a second substantially transparent layer which is formed over the first layer and has an optical thickness of approximately λ 0 /4, and an index of refraction between approximately 2.6 and 2.7; a third substantially transparent layer which is formed over the second layer and has an optical thickness of approximately λ 0 /4 and an index of refraction between approximately 1.9 and 2.0; and a fourth substantially transparent layer which is formed over the third layer and has an optical thickness of approximately λ 0 /4 and an index of refraction between approximately 1.4 and 1.5.
Claim 3
Dependent Claim
25 words
A coating as in claim 1, in which the first layer comprises a material selected from the group consisting of silicon (Si) and germanium (Ge).
Claim 4
Dependent Claim
23 words
A coating as in claim 1, in which the first layer comprises silicon (Si) and has a physical thickness of approximately 1,170 Å.
Claim 5
Dependent Claim
39 words
A coating as in claim 1, in which the second layer comprises a material selected from the group consisting of silicon suboxide (SiO 0<X<1 ), cadmium telluride (CdTe), silicon carbide (SiC) and silicon nitride (Si 3 N 4 ).
Claim 6
Dependent Claim
26 words
A coating as in claim 1, in which the second layer comprises silicon suboxide (SiO 0<X<1 ) and has a physical thickness of approximately 1,300 Å.
Claim 7
Dependent Claim
54 words
A coating as in claim 1, in which the third layer comprises a material selected from the group consisting of silicon monoxide (SiO), hafnium oxide (HfO 2 ), bismuth oxide (Bi 2 O 3 ), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ) and cadmium telluride oxide (CdTeO 3 ).
Claim 8
Dependent Claim
24 words
A coating as in claim 1, in which the third layer comprises silicon monoxide (SiO) and has a physical thickness of approximately 2,000 Å.
Claim 9
Dependent Claim
36 words
A coating as in claim 1, in which the fourth layer comprises a material selected from the group consisting of silicon dioxide (SiO 2 ), magnesium fluoride (MgF 2 ) and calcium fluoride (CaF 2 ).
Claim 10
Dependent Claim
26 words
A coating as in claim 1, in which the fourth layer comprises silicon dioxide (SiO 2 ) and has a physical thickness of approximately 2,400 Å.
Claim 11
Dependent Claim
62 words
A coating as in claim 1, further comprising a passivation layer formed on said surface underlying the first layer, the passivation layer comprising a material selected from the group consisting of silicon (Si), silicon monoxide (SiO), silicon dioxide (SiO 2 ), silicon suboxide (SiO 0<X<1 ), silicon nitride (Si 3 N 4 ), germanium (Ge), cadmium telluride (CdTe) and gallium arsenide (GaAs).
Claim 12
Dependent Claim
25 words
A coating as in claim 1, in which the passivation layer comprises germanium and has a physical thickness between approximately 50 Å and 150 Å.
Claim 13
Dependent Claim
14 words
A coating as in claim 1, in which λ 0 is approximately 1.6 microns.
Claim 14
Dependent Claim
161 words
A photodetector device, comprising: an indium antimonide (InSb) photodetector having a light-receiving surface; and an anti-reflection coating which is formed on said surface and includes: a first substantially transparent layer which is formed over said surface and has an optical thickness of approximately λ 0 /4, where λ 0 is a predetermined reference wavelength, and an index of refraction between approximately 3.2 and 3.3; a second substantially transparent layer which is formed over the first layer and has an optical thickness of approximately λ 0 /4, and an index of refraction between approximately 2.6 and 2.7; a third substantially transparent layer which is formed over the second layer and has an optical thickness of approximately λ 0 /4 and an index of refraction between approximately 1.9 and 2.0; and a fourth substantially transparent layer which is formed over the third layer and has an optical thickness of approximately λ 0 /4 and an index of refraction between approximately 1.4 and 1.5.
Claim 15
Dependent Claim
161 words
A photodetector device, comprising: an indium antimonide (InSb) photodetector having a light-receiving surface; and an anti-reflection coating which is formed on said surface and includes: a first substantially transparent layer which is formed over said surface and has an optical thickness of approximately λ 0 /4, where λ 0 is a predetermined reference wavelength, and an index of refraction between approximately 3.2 and 3.3; a second substantially transparent layer which is formed over the first layer and has an optical thickness of approximately λ 0 /4, and an index of refraction between approximately 2.6 and 2.7; a third substantially transparent layer which is formed over the second layer and has an optical thickness of approximately λ 0 /4 and an index of refraction between approximately 1.9 and 2.0; and a fourth substantially transparent layer which is formed over the third layer and has an optical thickness of approximately λ 0 /4 and an index of refraction between approximately 1.4 and 1.5.
Claim 16
Dependent Claim
25 words
A device as in claim 13, in which the first layer comprises a material selected from the group consisting of silicon (Si) and germanium (Ge).
Claim 17
Dependent Claim
23 words
A device as in claim 13 in which the first layer comprises silicon (Si) and has a physical thickness of approximately 1,170 Å.
Claim 18
Dependent Claim
39 words
A device as in claim 13, in which the second layer comprises a material selected from the group consisting of silicon suboxide (SiO 0<X<1 ), cadmium telluride (CdTe), silicon carbide (SiC) and silicon nitride (Si 3 N 4 ).
Claim 19
Dependent Claim
26 words
A device as in claim 13, in which the second layer comprises silicon suboxide (SiO 0<X<1 ) and has a physical thickness of approximately 1,300 Å.
Claim 20
Dependent Claim
54 words
A device as in claim 13, in which the third layer comprises a material selected from the group consisting of silicon monoxide (SiO), hafnium oxide (HfO 2 ), bismuth oxide (Bi 2 O 3 ), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ) and cadmium telluride oxide (CdTeO 3 ).
Claim 21
Dependent Claim
24 words
A device as in claim 13, in which the third layer comprises silicon monoxide (SiO) and has a physical thickness of approximately 2,000 Å.
Claim 22
Dependent Claim
36 words
A device as in claim 13, in which the fourth layer comprises a material selected from the group consisting of silicon dioxide (SiO 2 ), magnesium fluoride (MgF 2 ) and calcium fluoride (CaF 2 ).
Claim 23
Dependent Claim
26 words
A device as in claim 13, in which the fourth layer comprises silicon dioxide (SiO 2 ) and has a physical thickness of approximately 2,400 Å.
Claim 24
Dependent Claim
62 words
A device as in claim 13, further comprising a passivation layer formed on said surface underlying the first layer, the passivation layer comprising a material selected from the group consisting of silicon (Si), silicon monoxide (SiO), silicon dioxide (SiO 2 ), silicon suboxide (SiO 0<X<1 ), silicon nitride (Si 3 N 4 ), germanium (Ge), cadmium telluride (CdTe) and gallium arsenide (GaAs).
Claim 25
Dependent Claim
22 words
A device as in claim 22, in which the passivation layer has a physical thickness between approximately 50 Å and 150 Å.
Claim 26
Dependent Claim
14 words
A coating as in claim 13, in which λ 0 is approximately 1.6 microns.
References Cited (Backward Citations)
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