EP0043734A2
Expired / Lapsed
EP
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Avalanche photodiodes
Assignee: Fujitsu Ltd
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Filing: 1981-07-08
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Granted: —
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Expires: 2001-07-08
Abstract
Abstract The avalanche photodiode as a light absorbing layer 3 on top of which is a first window layer 4 on top of which is a second window layer 5. An upper region 6 of the second window layer 5 is relatively heavily doped with an impurity of a conductivity type different from that of the second window layer 5 to provide a p-n junction for avalanche multiplication in the second window layer 5. Around the p-n junction for avalanche multiplication the second window layer 5 and an upper region of the first window layer4 are relatively heavily doped to provide a p-n junction for a guard ring effect in the first window layer 4. p-n Junction 9, in the first window layer 4, for the guard ring effect is approximately 0.5 micrometers above the heterojunction 11 between the light absorbing layer 3 and the first window layer 4. The p-n junction 10 for avalanche multiplication is approximately 1.5 micrometers above the heterojunction 11. A method of manufacturing such an avalanche photodiode is provided in which only one diffusion step is required for forming the p-n junctions 9 and 10 to different depths.
Inventors
- 👤 Fukunobu Osaka
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 23:51
CPC Classifications
H; H10; H10F; H10F30/00; H10F30/20; H10F30/21; H10F30/22; H10F30/225; H10F30/2255
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
265 words
An avalanche photodiode comprising: a light absorbing layer of a semiconductor doped with an impurity of one conductivity type, a first window layer of a semiconductor having a larger band gap than that of the light absorbing layer, doped with an impurity of the same conductivity type as that of the impurity of the light absorbing layer, to a concentration at least similar to that of the light absorbing layer, and formed on top of the light absorbing layer, and a second window layer of the same semiconductor as that of the first window layer, doped with an impurity of the same conductivity type as the impurity of the first window layer, to a concentration higher than that of the first window layer, and formed on a limited area of the top surface of the first window layer, an upper region of the second window layer being doped with an impurity of a conductivity type different from that of the impurity of the second window layer, to a relatively high concentration, to provide a p-n junction for avalanche multiplication and to provide a light sensitive region, the perimeter of the second window layer and an upper region of the first window layer surrounding the perimeter of the second window layer being doped with an impurity of the same conductivity type as that of the upper region of the second window layer, to a relatively high concentration, and to a depth a specific distance above.the'hetero junction between the light absorbing layer and the first window layer, to provide a p-n junction for a guard ring effect.
Claim 2
Dependent Claim
265 words
An avalanche photodiode comprising: a light absorbing layer of a semiconductor doped with an impurity of one conductivity type, a first window layer of a semiconductor having a larger band gap than that of the light absorbing layer, doped with an impurity of the same conductivity type as that of the impurity of the light absorbing layer, to a concentration at least similar to that of the light absorbing layer, and formed on top of the light absorbing layer, and a second window layer of the same semiconductor as that of the first window layer, doped with an impurity of the same conductivity type as the impurity of the first window layer, to a concentration higher than that of the first window layer, and formed on a limited area of the top surface of the first window layer, an upper region of the second window layer being doped with an impurity of a conductivity type different from that of the impurity of the second window layer, to a relatively high concentration, to provide a p-n junction for avalanche multiplication and to provide a light sensitive region, the perimeter of the second window layer and an upper region of the first window layer surrounding the perimeter of the second window layer being doped with an impurity of the same conductivity type as that of the upper region of the second window layer, to a relatively high concentration, and to a depth a specific distance above.the'hetero junction between the light absorbing layer and the first window layer, to provide a p-n junction for a guard ring effect.
Claim 3
Dependent Claim
38 words
An avalanche photodiode as claimed in claim 1, in which the light absorbing layer is grown on top of a semiconductor substrate of the photodiode, or on top of a buffer layer grown on top of the substrate.
Claim 4
Dependent Claim
31 words
An avalanche photodiode as claimed in claim-2, in which a first electrode is formed on the second window layer, and a second electrode is formed on the underside of the substrate.
Claim 5
Dependent Claim
50 words
An avalanche photodiode as claimed in any preceding claim, in which the light absorbing layer is of InGaAsp or InGaAs, for example doped with an n-type impurity, or is of GaSb, and the first window layer is of InP, for example doped with an n-type impurity, or is of GaAsSb.
Claim 6
Dependent Claim
37 words
An avalanche photodiode as claimed in any preceding claim, in which the said specific distance is approximately 0.5 micrometers, and the distance from the p-n junction for avalanche multiplication to the said heterojunction is approximately 1.5 micrometers.
Claim 7
Independent Claim
227 words
A method of producing an avalanche photodiode, the method comprising: a step for growing a light absorbing layer of a semiconductor doped with an impurity of one conductivity type, a step for growing a first window layer of a semiconductor having a larger band gap than that of the semiconductor of the light absorbing layer and which is doped with an impurity of the same conductivity type as that of the light absorbing layer, to a concentration at least similar to that of the light absorbing layer, on top of the light absorbing layer, a step for growing a second window layer of the same semiconductor as that of the first window layer and which is doped with an impurity of the same conductivity type as that of the first window layer, to a concentration higher than that of the first window layer, on top of the first window layer, a step for removing a limited portion of the second window layer to produce a mesa configuration for the second window layer, and a step for providing a relatively high doping concentration of an impurity of a different conductivity type from that of the second window layer in an upper region of the mesa of the second window layer and in an upper region of the first window layer surrounding the mesa of the second window layer.
Claim 8
Independent Claim
227 words
A method of producing an avalanche photodiode, the method comprising: a step for growing a light absorbing layer of a semiconductor doped with an impurity of one conductivity type, a step for growing a first window layer of a semiconductor having a larger band gap than that of the semiconductor of the light absorbing layer and which is doped with an impurity of the same conductivity type as that of the light absorbing layer, to a concentration at least similar to that of the light absorbing layer, on top of the light absorbing layer, a step for growing a second window layer of the same semiconductor as that of the first window layer and which is doped with an impurity of the same conductivity type as that of the first window layer, to a concentration higher than that of the first window layer, on top of the first window layer, a step for removing a limited portion of the second window layer to produce a mesa configuration for the second window layer, and a step for providing a relatively high doping concentration of an impurity of a different conductivity type from that of the second window layer in an upper region of the mesa of the second window layer and in an upper region of the first window layer surrounding the mesa of the second window layer.
Claim 9
Dependent Claim
60 words
A method as claimed in claim 6, in which the light absorbing layer is grown on top of a semiconductor substrate of the photodiode, or on top of a buffer layer grown on top of the substrate, the substrate being doped with an impurity of the same conductivity type as the impurity with which the light absorbing layer is doped.
Claim 10
Dependent Claim
38 words
A method as claimed in claim 7, comprising a step for growing a first electrode on the mesa of the second window layer, and a step for growing a second electrode on the under side of the substrate.
Claim 11
Independent Claim
52 words
A method as claimed in any one of claims 6 to 8, in which the light absorbing layer is of InGaAsP or InGaAs, for example doped with an n-impurity, or is of GaSb, and the first window layer is of InP, for example doped with an n-type impurity, or is of GaAsSb.
Claim 12
Independent Claim
67 words
A method as claimed in any one of claims 6 to 9, in which the said upper region of the first window layer extends to a depth approximately 0.5 micrometers above the heterojinction between the light absorbing layer and the first window layer, and the said upper region of the mesa of the second window layer extends to a depth approximately 1.5 micrometers above the said heterojunction
References Cited (Backward Citations)
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