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US 5,093,576 AGranted
High sensitivity ultraviolet radiation detector
AssigneeCree Research, Inc.
InventorsJohn A. Edmond, Calvin H. Carter, Jr.
Life of this patent
Estimating the term…
Abstract
A high sensitivity radiation detecting photodiode formed in silicon carbide comprises a monocrystalline silicon carbide substrate; a first monocrystalline portion of silicon carbide upon the substrate and having a first conductivity type; a second monocrystalline portion of silicon carbide adjacent the first portion and having the opposite conductivity type from the first portion; and a p-n junction between the adjacent first and second portions. The photodiode provides a dark current density of no more than about 1.times.10.sup.-9 amps/cm.sup.2 at a reverse bias of -1.0 volts and at temperatures of 170.degree. C. or less.
Claims27
A high sensitivity ultraviolet radiation detecting photodiode formed in silicon carbide and comprising:
- a single crystal substrate of silicon carbide having a first conductivity type;
- a first epitaxial layer of silicon carbide upon said substrate and having the same conductivity type as said substrate;
- a top epitaxial layer of silicon carbide upon said first epitaxial layer for being exposed to incident electromagnetic radiation, and having the opposite conductivity type from said first layer and said substrate;
- said first epitaxial layer and said top epitaxial layer forming a p-n junction therebetween;
- said first layer having a carrier concentration sufficiently lower than the carrier concentration of said top layer so that the depletion region of said p-n junction forms predominantly in said first layer at equilibrium;
- said first layer further having a defined thickness that is sufficient to support said depletion region and that is greater than the diffusion length of minority carriers in said first layer so that electron-hole pairs generated by photons absorbed in said first layer will diffuse to said depletion region within their carrier lifetimes;
- said top epitaxial layer having a defined thickness less than the thickness of said first layer and that is larger than the zero bias depletion layer width in said top layer while small enough to avoid substantial absorption of ultraviolet radiation in said top layer and thin enough so that radiation in the ultraviolet range generates carriers predominantly in said depletion region of said p-n junction;
- said top epitaxial layer further having a carrier concentration large enough to substantially reduce the series and sheet resistance;
- and
- ohmic contacts to said top epitaxial layer and to said substrate.
7 more elements
A high sensitivity ultraviolet radiation detecting photodiode formed in silicon carbide and comprising:
- a single crystal substrate of silicon carbide having a first conductivity type;
- an additional epitaxial layer of silicon carbide upon said substrate and having the opposite conductivity type from said substrate;
- a first epitaxial layer of silicon carbide upon said additional epitaxial layer and having the same conductivity type as said additional epitaxial layer;
- a top epitaxial layer of silicon carbide upon said first epitaxial layer for being exposed to incident electromagnetic radiation, and having the opposite conductivity type from said first layer and said additional layer;
- said first epitaxial layer and said top epitaxial layer forming a p-n junction therebetween;
- said first layer having a carrier concentration sufficiently lower than the carrier concentration of said top layer so that the depletion region of said p-n junction forms predominantly in said first layer at equilibrium;
- said first layer further having a defined thickness that is sufficient to support said depletion region and that is greater than the diffusion length of minority carriers in said first layer so that electron-hole pairs generated by photons absorbed in said first layer will diffuse to said depletion region within their carrier lifetimes;
- said top epitaxial layer having a defined thickness less than the thickness of said first layer and that is larger than the zero bias depletion layer width in said top layer while small enough to avoid substantial absorption of ultraviolet radiation in said top layer and thin enough so that radiation in the ultraviolet range generates carriers predominantly in said depletion region of said p-n junction;
- said top epitaxial layer further having a carrier concentration large enough to substantially reduce the series and sheet resistance;
- and
- ohmic contacts to said top epitaxial layer and to said substrate.
8 more elements
A high sensitivity ultraviolet radiation detecting photodiode formed in silicon carbide and comprising:
- a single crystal substrate of alpha silicon carbide having a first conductivity type;
- a first epitaxial layer of silicon carbide upon said substrate and having the same conductivity type as said substrate;
- a top epitaxial layer of silicon carbide upon said first epitaxial layer and having the opposite conductivity type from said first layer and said substrate, said top layer having a thickness of no more than about 300 nanometers;
- a p-n junction between said first epitaxial layer and said top epitaxial layer;
- and
- ohmic contacts to said substrate and to said top layer.
3 more elements
A high sensitivity ultraviolet radiation detecting photodiode formed in silicon carbide and comprising:
- a single crystal substrate of alpha silicon carbide having a first conductivity type;
- an additional epitaxial layer of silicon carbide upon said substrate and having the opposite conductivity type from said substrate;
- a first epitaxial layer of silicon carbide upon said additional epitaxial layer and having the same conductivity type as said additional epitaxial layer;
- a top epitaxial layer of silicon carbide upon said first epitaxial layer and having the opposite conductivity type from said first layer and said additional layer, said top layer having a thickness of no more than about 300 nanometers;
- a p-n junction between said first epitaxial layer and said top epitaxial layer;
- and
- ohmic contacts to said substrate and to said top layer.
4 more elements
A high sensitivity radiation detecting photodiode formed in silicon carbide and comprising:
- a monocrystalline silicon carbide substrate
- a first monocrystalline portion of silicon carbide upon said substrate and having a first conductivity type;
- a second monocrystalline portion of silicon carbide adjacent said first portion and having the opposite conductivity type from said first portion;
- and
- a p-n junction between said adjacent first and second portions for providing a dark current density of no more than about 1.times.10.sup.-9 amps/cm.sup.2 at a reverse bias of -1.0 volts and at temperatures of 170.degree. C. or less.
2 more elements
A method of detecting and measuring ultraviolet radiation, the method comprising:
- exposing a photodiode to electromagnetic radiation wherein the photodiode is formed of adjacent regions of silicon carbide having respective p-type and n-type conductivities with a p-n junction between the respective regions and wherein the diode has a dark current density of no more than about 1.times.10.sup.-9 amps/cm.sup.-2 at a reverse bias of -1.0 volts and at temperatures of 170.degree. C. or less.
Dependencies are inferred from the claim text.