Patent EP0087299A2 successfully refreshed from Google Patents.
EP0087299A2
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EP
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Multilayer avalanche photodetector
Assignee: Trasformazione Societaria at & T Technologies Inc
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Filing: 1983-02-21
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Granted: —
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Expires: 2003-02-21
Abstract
Abstract The avalanche region of a photodetector comprises layers (31, 33, 35,37) in which the bandgap is graded, with steps back from the wider gap to the narrower gap. The preferred carriers (electrons) are rapidly accelerated in the regions of the steps, so that the probability of an electron causing an impact ionization in the narrow-gap region just past each step is high. The non-preferred carriers (holes) undergo a comparatively uniform acceleration and are thus more likely to lose energy by optical phonon emission. They are therefore less likely to cause impact ionizations. The device noise is thus reduced. Also, the necessary bias voltage is reduced.
Inventors
- 👤 Federico Capasso
- 👤 Won-Tien Tsang
- 👤 Gareth Ferd Williams
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 22:34
CPC Classifications
H; H10; H10F; H10F30/00; H10F30/20; H10F30/21; H10F30/22; H10F30/222; H10F30/225; H10F30/2255
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
83 words
An avalanche photodetector comprising a first layer (3) having a first conductivity type, a second layer (7) having a second conductivity type and, disposed intermediate the first layer (3) and the second layer (7), at least one compositionally varying layer (11,13,15,17,19) having a composition varying from a narrow bandgap composition to a wide bandgap composition, characterised in that the at least one compositionally varying layer has an energy band step back after the wide bandgap that assists ionization of one type of carrier.
Claim 2
Dependent Claim
83 words
An avalanche photodetector comprising a first layer (3) having a first conductivity type, a second layer (7) having a second conductivity type and, disposed intermediate the first layer (3) and the second layer (7), at least one compositionally varying layer (11,13,15,17,19) having a composition varying from a narrow bandgap composition to a wide bandgap composition, characterised in that the at least one compositionally varying layer has an energy band step back after the wide bandgap that assists ionization of one type of carrier.
Claim 3
Dependent Claim
30 words
A photodetector as claimed in claim 1 in which the at least one compositionally varying layer is substantially continuously graded between the narrow bandgap composition and the wide bandgap composition.
Claim 4
Dependent Claim
18 words
A photodetector as claimed in claim 2 in which the continuous grading is a substantially linear compositional variation.
Claim 5
Dependent Claim
43 words
A photodetector as claimed in claim 1, 2 or 3 in which the energy band step back is approximately equal to or greater than the ionization energy of the said one type of carrier in the narrow gap material after the step back.
Claim 6
Dependent Claim
31 words
A photodetector as claimed in any of the preceding claims in which the energy band step back is primarily in the conduction band, the said one type of carrier being electrons.
Claim 7
Dependent Claim
18 words
A photodetector as claimed in any of the preceding claims in which the step back is substantially abrupt.
Claim 8
Dependent Claim
47 words
A photodetector as claimed in any of the preceding claims in which the at least one compositionally graded layer further comprises an ungraded or slowly graded narrow gap region (43) adjacent to the energy band step back whereby the number of carriers that cause ionization is increased.
Claim 9
Dependent Claim
31 words
A photodetector as claimed in claim 7, wherein the at least one compositionally varying layer has spacially varying doping arranged to reduce the electric field in said narrow gap region (43).
Claim 10
Dependent Claim
43 words
A photodetector as claimed in any of the preceding claims wherein the at least one compositionally varying layer has spacially varying doping arranged to increase the electric field in the neighbourhood of the energy band step back when the photodetector is in use.
Claim 11
Dependent Claim
48 words
A photodetector as claimed in any of the preceding claims in which the at least one compositionally graded layer further comprises an ungraded or slowly graded wide gap region (53) adjacent to the energy band step back whereby the average carrier energy above the band edge is increased.
References Cited (Backward Citations)
No citation records indexed.
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