US20160020339A1 - Light receiving element - Google Patents
Light receiving element Download PDFInfo
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- US20160020339A1 US20160020339A1 US14/682,953 US201514682953A US2016020339A1 US 20160020339 A1 US20160020339 A1 US 20160020339A1 US 201514682953 A US201514682953 A US 201514682953A US 2016020339 A1 US2016020339 A1 US 2016020339A1
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- light absorbing
- light
- receiving element
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- 239000000758 substrate Substances 0.000 claims abstract description 53
- 238000009792 diffusion process Methods 0.000 claims abstract description 35
- 239000000969 carrier Substances 0.000 claims description 15
- 239000002184 metal Substances 0.000 claims description 12
- 229910052751 metal Inorganic materials 0.000 claims description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 230000003111 delayed effect Effects 0.000 description 5
- 229910052681 coesite Inorganic materials 0.000 description 3
- 229910052906 cristobalite Inorganic materials 0.000 description 3
- 229910052737 gold Inorganic materials 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 229910052682 stishovite Inorganic materials 0.000 description 3
- 229910052905 tridymite Inorganic materials 0.000 description 3
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 229910008062 Si-SiO2 Inorganic materials 0.000 description 1
- 229910006403 Si—SiO2 Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000002513 implantation Methods 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 238000005468 ion implantation Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0216—Coatings
- H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0216—Coatings
- H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/02162—Coatings for devices characterised by at least one potential jump barrier or surface barrier for filtering or shielding light, e.g. multicolour filters for photodetectors
- H01L31/02164—Coatings for devices characterised by at least one potential jump barrier or surface barrier for filtering or shielding light, e.g. multicolour filters for photodetectors for shielding light, e.g. light blocking layers, cold shields for infrared detectors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
- H01L31/035272—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
- H01L31/035281—Shape of the body
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
- H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
- H01L31/109—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the PN heterojunction type
Definitions
- the present invention relates to a light receiving element for use in optical communication for example.
- Japanese Patent Laid-Open No. 2010-45417 discloses a light receiving element having an anode electrode on the upper surface side of a substrate, and a cathode electrode on a lower surface of the substrate.
- Japanese Patent Laid-Open No. 2007-88496 discloses a light receiving element having an anode electrode and a cathode electrode on the upper surface side of a substrate.
- Increasing the response speed of a light receiving element requires eliminating a “current component delayed in response” which is a current component generated after a lapse of a certain time period from a time at which light enters the light receiving element.
- a “current component delayed in response” which is a current component generated after a lapse of a certain time period from a time at which light enters the light receiving element.
- the present invention has been achieved to solve the above-described problems, and an object of the present invention is to provide a light receiving element capable of having an increased response speed preventing a short circuit between the anode electrode and the cathode electrode.
- a light receiving element includes a substrate of a first conduction type, a light absorbing layer of the first conduction type formed on the substrate and having a bandgap smaller than that of the substrate, a diffusion layer of a second conduction type formed on a portion of the light absorbing layer, a window layer of the first conduction type formed on the light absorbing layer so as to surround the diffusion layer and having a bandgap larger than that of the light absorbing layer, an anode electrode formed on the diffusion layer, and a cathode electrode provided on the substrate so as to contact the substrate without contacting each of the window layer and the light absorbing layer, wherein a groove is formed which surrounds a boundary between the diffusion layer and the window layer as viewed in plan and extends through the window layer and the light absorbing layer as viewed in section.
- a light receiving element includes a substrate of a first conduction type, a light absorbing layer of the first conduction type formed on the substrate and having a bandgap smaller than that of the substrate, a diffusion layer of a second conduction type formed on a portion of the light absorbing layer, a window layer of the first conduction type formed on the light absorbing layer so as to surround the diffusion layer and having a bandgap larger than that of the light absorbing layer, an anode electrode formed on the diffusion layer, a cathode electrode provided on the substrate so as to contact the substrate without contacting each of the window layer and the light absorbing layer, and an ion-implanted portion surrounding a boundary between the diffusion layer and the window layer as viewed in plan, extending through the window layer and the light absorbing layer as viewed in section, and shutting off a flow of carriers.
- FIG. 1 is a sectional view of a light receiving element according to a first embodiment
- FIG. 2 is a plan view of the light receiving element
- FIG. 3 is a sectional view of a light receiving element according to a second embodiment
- FIG. 4 is a sectional view of a light receiving element according to a third embodiment.
- FIG. 5 is a plan view of the light receiving element shown in FIG. 4 .
- FIG. 1 is a sectional view of a light receiving element 10 according to a first embodiment of the present invention.
- the light receiving element 10 has a substrate 12 of a first conduction type.
- the substrate 12 is, for example, n-type InP.
- a light absorbing layer 14 of the first conduction type is formed on the substrate 12 .
- the light absorbing layer 14 has a bandgap smaller than that of the substrate 12 .
- the light absorbing layer 14 is, for example, n-type InGaAs.
- a diffusion layer 16 of a second conduction type is formed on a portion of the light absorbing layer 14 .
- the diffusion layer 16 is, for example, p-type InP.
- a window layer 18 of the first conduction type is formed on the light absorbing layer 14 .
- the window layer 18 is formed so as to surround the diffusion layer 16 as viewed in plan.
- the window layer 18 has a bandgap larger than that of the light absorbing layer 14 .
- the window layer 18 is, for example, n-type InP.
- Grooves 20 and 22 are formed on the upper surface side of the substrate 12 .
- the groove 20 surrounds a boundary 23 between the diffusion layer 16 and the window layer 18 as viewed in plan, and extends through the window layer 18 and the light absorbing layer 14 as viewed in section.
- the groove 22 is formed outside the groove 20 .
- the groove 22 extends through the window layer 18 and the light absorbing layer 14 as viewed in section.
- An insulating film 24 is formed on the upper surface side of the light receiving element 10 .
- the insulating film 24 is formed on the upper surface of the window layer 18 and in the grooves 20 and 22 .
- the insulating film 24 in the groove 20 abuts the window layer 18 , the light absorbing layer 14 and the substrate 12 .
- the material of the insulating film 24 is, for example, SiN.
- the insulating film 24 has an opening right above the diffusion layer 16 .
- An anode electrode 26 is formed on the diffusion layer 16 .
- the insulating film 24 in the groove 22 has an opening in its lower end portion.
- a cathode electrode 28 is provided in this opening so as to contact the substrate 12 .
- the cathode electrode 28 is provided on (above) the substrate 12 .
- the cathode electrode 28 abuts the insulating film 24 in the groove 22 and does not contact the window layer 18 and the light absorbing layer 14 .
- the anode electrode 26 and the cathode electrode 28 are each formed, for example, of a multilayer structure including Ti and Au, i.e., Ti/Au (the material on the left-hand side of the symbol “/” is closer to the substrate, materials shown in the same way below), Ti/Pt/Au, Pt/Ti/Pt/Au, or the like.
- a portion of a lower surface of the substrate 12 is covered with a metal mask 30 .
- the metal mask 30 is made of the material which does not transmits light.
- the metal mask 30 is formed, for example, of a multilayer structure including Ti and Au, i.e., AuGe/Ni/Ti/Pt/Au, AuZn/Ti/Pt/Au, or the like.
- the metal mask 30 is not formed right below the diffusion layer 16 . That is, the metal mask 30 has an opening right below the diffusion layer 16 .
- a low-reflection film 32 is formed in this opening so as to contact the lower surface of the substrate 12 .
- the low-reflection film 32 allows light to pass therethrough without reflecting light.
- the low-reflection film 32 is not particularly specified in other respects.
- the low-reflection film 32 is formed, for example, an Si-SiO 2 multilayer structure, i.e., Si/SiO 2 , Si/SiO 2 /Si/SiO 2 , or the like.
- FIG. 2 is a plan view of the light receiving element 10 .
- the groove 20 surrounds the boundary 23 between the diffusion layer 16 and the window layer 18 as viewed in plan.
- the boundary 23 is indicated by a broken line.
- the outer circumference of the low-reflection film 32 is also indicated by a broken line.
- the outer circumference of the low- reflection film 32 and the inner circumference of the groove 20 are superposed on each other.
- FIG. 1 is a sectional view taken along a line indicated by a dot-dash line in FIG. 2 .
- a reverse bias is applied to the pn junction between the diffusion layer 16 and the window layer 18 and the pn junction between the diffusion layer 16 and the light absorbing layer 14 to form a depletion layer.
- light enters the light receiving element 10 from a direction indicated by an arrow in FIG. 1 .
- the light having entered generates carriers (electrons and holes) in the light absorbing layer 14 .
- the generated carriers are accelerated by the depletion layers to flow to the anode electrode 26 or the cathode electrode 28 . As a result, a current is detected.
- Carriers move through a long distance and become a current component after a lapse of a certain time period from the time at which light enters the light receiving element, which means degradation in response of the light receiving element. That is, if carriers having moved through a long distance contribute to the detected current, a current component delayed in response will be generated.
- the thickness of the substrate 12 is increased to a thickness of about several hundred microns for example.
- the cathode electrode 28 is provided on the upper surface side of the substrate 12 , so that the carrier travel distance is not increased even when the thickness of the substrate 12 is increased, thus enabling prevention of a current component delayed in response.
- anode electrode 26 and the cathode electrode 28 are provided on the upper surface side of the substrate 12 , mounting of the light receiving element 10 is completed by only die-bonding the element to a submount.
- the cathode electrode is formed on the lower surface of the substrate while the anode electrode is formed on the upper surface of the substrate, it is necessary to fix the anode electrode on the submount before wire bonding on the cathode electrode.
- the cathode electrode is formed in the groove 20 , there is a risk of a short circuit between the anode electrode and the cathode electrode. According to the first embodiment of the present invention, however, the problem of a short circuit between the anode electrode 26 and the cathode electrode 28 can be avoided since the groove 20 exists between these electrodes.
- the light receiving element 10 according to the first embodiment of the present invention can be variously modified.
- the outer circumference of the low-reflection film 32 (the opening of the metal mask 30 ) may be set larger than the inner circumference of the groove 20 since only light entering the region surrounded by the groove 20 contributes to the detected current.
- the entire pn junction can be used for current generation.
- the entire lower surface of the substrate 12 may be used as a light receiving surface by omitting the metal mask 30 .
- the amount of light blocked by the metal mask 30 can be reduced by increasing the opening of the metal mask 30 or omitting the metal mask 30 , resulting in reduction of the light-electricity conversion loss.
- first conduction type and the second conduction type are assumed to be the n-type and the p-type, respectively, the conduction types may be reversed.
- a buffer layer and the like may be provided between the layers.
- FIG. 3 is a sectional view of a light receiving element according to a second embodiment of the present invention.
- a portion of the lower surface of the substrate 12 is covered with an epitaxial layer 60 .
- the material of the epitaxial layer 60 is not particularly limited as long as it is capable of absorbing light. However, the material of the epitaxial layer 60 is, for example, n-type InGaAs.
- the epitaxial layer 60 has an opening right below the diffusion layer 16 . A low-reflection film 62 is formed in this opening.
- the metal mask 30 in the first embodiment reflects light and there is a possibility of the reflected light interfering with the incident light. However, in the second embodiment of the present invention, such reflection of light can be prevented since the epitaxial layer 60 capable of absorbing light is formed.
- FIG. 4 is a sectional view of a light receiving element according to a third embodiment of the present invention.
- This light receiving element is provided with an ion-implanted portion 70 formed, for example, by implantation with Ti and the like.
- the ion-implanted portion 70 surrounds the boundary between the diffusion layer 16 and the window layer 18 as viewed in plan, and extends through the window layer 18 and the light absorbing layer 14 as viewed in section.
- FIG. 5 is a plan view of the light receiving element shown in FIG. 4 .
- the ion-implanted portion 70 indicated by a broken line surrounds the boundary 23 between the diffusion layer and the window layer as viewed in plan.
- the ion-implanted portion 70 has the same function as that of the groove 20 in the first embodiment.
- the ion-implanted portion 70 can easily be made by only performing ion implantation after the window layer 18 is formed.
- a suitable combination of the features of the light receiving elements according to the embodiments described above may be made and used.
- the anode electrode and the cathode electrode are formed on the upper surface side of the substrate and a groove or an ion-implanted portion is formed between the anode electrode and the cathode electrode, thereby enabling increasing the response speed and preventing a short circuit between the anode electrode and the cathode electrode.
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Abstract
Description
- 1. Field of the Invention
- The present invention relates to a light receiving element for use in optical communication for example.
- 2. Background Art
- Japanese Patent Laid-Open No. 2010-45417 discloses a light receiving element having an anode electrode on the upper surface side of a substrate, and a cathode electrode on a lower surface of the substrate. Japanese Patent Laid-Open No. 2007-88496 discloses a light receiving element having an anode electrode and a cathode electrode on the upper surface side of a substrate.
- Increasing the response speed of a light receiving element requires eliminating a “current component delayed in response” which is a current component generated after a lapse of a certain time period from a time at which light enters the light receiving element. With the light receiving element disclosed in Japanese Patent Laid-Open No. 2010-45417, there is a problem that if the thickness of the substrate is increased, the distance through which carriers travel is increased and the response speed is reduced. In the light receiving element disclosed in Japanese Patent Laid-Open No. 2007-88496, the anode electrode and the cathode electrode are adjacent to each other and there is a possibility of a short circuit between the anode electrode and the cathode electrode.
- The present invention has been achieved to solve the above-described problems, and an object of the present invention is to provide a light receiving element capable of having an increased response speed preventing a short circuit between the anode electrode and the cathode electrode.
- The features and advantages of the present invention may be summarized as follows.
- According to one aspect of the present invention, a light receiving element includes a substrate of a first conduction type, a light absorbing layer of the first conduction type formed on the substrate and having a bandgap smaller than that of the substrate, a diffusion layer of a second conduction type formed on a portion of the light absorbing layer, a window layer of the first conduction type formed on the light absorbing layer so as to surround the diffusion layer and having a bandgap larger than that of the light absorbing layer, an anode electrode formed on the diffusion layer, and a cathode electrode provided on the substrate so as to contact the substrate without contacting each of the window layer and the light absorbing layer, wherein a groove is formed which surrounds a boundary between the diffusion layer and the window layer as viewed in plan and extends through the window layer and the light absorbing layer as viewed in section.
- According to another aspect of the present invention, a light receiving element includes a substrate of a first conduction type, a light absorbing layer of the first conduction type formed on the substrate and having a bandgap smaller than that of the substrate, a diffusion layer of a second conduction type formed on a portion of the light absorbing layer, a window layer of the first conduction type formed on the light absorbing layer so as to surround the diffusion layer and having a bandgap larger than that of the light absorbing layer, an anode electrode formed on the diffusion layer, a cathode electrode provided on the substrate so as to contact the substrate without contacting each of the window layer and the light absorbing layer, and an ion-implanted portion surrounding a boundary between the diffusion layer and the window layer as viewed in plan, extending through the window layer and the light absorbing layer as viewed in section, and shutting off a flow of carriers.
- Other and further objects, features and advantages of the invention will appear more fully from the following description.
-
FIG. 1 is a sectional view of a light receiving element according to a first embodiment; -
FIG. 2 is a plan view of the light receiving element; -
FIG. 3 is a sectional view of a light receiving element according to a second embodiment; -
FIG. 4 is a sectional view of a light receiving element according to a third embodiment; and -
FIG. 5 is a plan view of the light receiving element shown inFIG. 4 . - A light receiving element according to embodiments of the present invention will be described with reference to the drawings. The same or corresponding components are given the same numerals and repetition of the description may be omitted.
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FIG. 1 is a sectional view of alight receiving element 10 according to a first embodiment of the present invention. Thelight receiving element 10 has asubstrate 12 of a first conduction type. Thesubstrate 12 is, for example, n-type InP. Alight absorbing layer 14 of the first conduction type is formed on thesubstrate 12. Thelight absorbing layer 14 has a bandgap smaller than that of thesubstrate 12. Thelight absorbing layer 14 is, for example, n-type InGaAs. - A
diffusion layer 16 of a second conduction type is formed on a portion of thelight absorbing layer 14. Thediffusion layer 16 is, for example, p-type InP. Awindow layer 18 of the first conduction type is formed on thelight absorbing layer 14. Thewindow layer 18 is formed so as to surround thediffusion layer 16 as viewed in plan. Thewindow layer 18 has a bandgap larger than that of thelight absorbing layer 14. Thewindow layer 18 is, for example, n-type InP. -
Grooves substrate 12. Thegroove 20 surrounds aboundary 23 between thediffusion layer 16 and thewindow layer 18 as viewed in plan, and extends through thewindow layer 18 and thelight absorbing layer 14 as viewed in section. Thegroove 22 is formed outside thegroove 20. Thegroove 22 extends through thewindow layer 18 and thelight absorbing layer 14 as viewed in section. - An
insulating film 24 is formed on the upper surface side of thelight receiving element 10. Theinsulating film 24 is formed on the upper surface of thewindow layer 18 and in thegrooves insulating film 24 in thegroove 20 abuts thewindow layer 18, thelight absorbing layer 14 and thesubstrate 12. The material of theinsulating film 24 is, for example, SiN. - The
insulating film 24 has an opening right above thediffusion layer 16. Ananode electrode 26 is formed on thediffusion layer 16. Theinsulating film 24 in thegroove 22 has an opening in its lower end portion. Acathode electrode 28 is provided in this opening so as to contact thesubstrate 12. Thecathode electrode 28 is provided on (above) thesubstrate 12. Thecathode electrode 28 abuts theinsulating film 24 in thegroove 22 and does not contact thewindow layer 18 and thelight absorbing layer 14. Theanode electrode 26 and thecathode electrode 28 are each formed, for example, of a multilayer structure including Ti and Au, i.e., Ti/Au (the material on the left-hand side of the symbol “/” is closer to the substrate, materials shown in the same way below), Ti/Pt/Au, Pt/Ti/Pt/Au, or the like. - A portion of a lower surface of the
substrate 12 is covered with ametal mask 30. Themetal mask 30 is made of the material which does not transmits light. However, themetal mask 30 is formed, for example, of a multilayer structure including Ti and Au, i.e., AuGe/Ni/Ti/Pt/Au, AuZn/Ti/Pt/Au, or the like. Themetal mask 30 is not formed right below thediffusion layer 16. That is, themetal mask 30 has an opening right below thediffusion layer 16. A low-reflection film 32 is formed in this opening so as to contact the lower surface of thesubstrate 12. The low-reflection film 32 allows light to pass therethrough without reflecting light. The low-reflection film 32 is not particularly specified in other respects. However, the low-reflection film 32 is formed, for example, an Si-SiO2 multilayer structure, i.e., Si/SiO2, Si/SiO2/Si/SiO2, or the like. -
FIG. 2 is a plan view of thelight receiving element 10. Thegroove 20 surrounds theboundary 23 between thediffusion layer 16 and thewindow layer 18 as viewed in plan. Theboundary 23 is indicated by a broken line. InFIG. 2 , the outer circumference of the low-reflection film 32 is also indicated by a broken line. The outer circumference of the low-reflection film 32 and the inner circumference of thegroove 20 are superposed on each other.FIG. 1 is a sectional view taken along a line indicated by a dot-dash line inFIG. 2 . - The operation of the
light receiving element 10 will be described. A reverse bias is applied to the pn junction between thediffusion layer 16 and thewindow layer 18 and the pn junction between thediffusion layer 16 and thelight absorbing layer 14 to form a depletion layer. In this state, light enters thelight receiving element 10 from a direction indicated by an arrow inFIG. 1 . The light having entered generates carriers (electrons and holes) in thelight absorbing layer 14. The generated carriers are accelerated by the depletion layers to flow to theanode electrode 26 or thecathode electrode 28. As a result, a current is detected. - It is preferable that when carriers are generated by light, they are rapidly detected as a current. In ordinary light receiving elements, however, the distance through which carriers generated in a place remote from the depletion layer (diffusion layer) move is long and the time taken for the carriers to move before being detected as a current is considerably long. Carriers move through a long distance and become a current component after a lapse of a certain time period from the time at which light enters the light receiving element, which means degradation in response of the light receiving element. That is, if carriers having moved through a long distance contribute to the detected current, a current component delayed in response will be generated.
- In the
light receiving element 10 according to the first embodiment of the present invention, however, carriers generated by light entering the element outside the region surrounded by thegroove 20 cannot reach the depletion layer because of the existence of thegroove 20. Therefore, even when light enters outside the region surrounded by thegroove 20, carriers generated by the light do not contribute to the detected current. Thus, the generation of a current component delayed in response can be prevented. - In some cases of optical system design, the thickness of the
substrate 12 is increased to a thickness of about several hundred microns for example. In such a case, if the cathode electrode is provided on the lower surface of thesubstrate 12, it is necessary for carriers to travel through the thick substrate, resulting in generation of a current component delayed in response. In contrast, in thelight receiving element 10 according to the embodiment of the present invention, thecathode electrode 28 is provided on the upper surface side of thesubstrate 12, so that the carrier travel distance is not increased even when the thickness of thesubstrate 12 is increased, thus enabling prevention of a current component delayed in response. - Since the
anode electrode 26 and thecathode electrode 28 are provided on the upper surface side of thesubstrate 12, mounting of thelight receiving element 10 is completed by only die-bonding the element to a submount. In the case where the cathode electrode is formed on the lower surface of the substrate while the anode electrode is formed on the upper surface of the substrate, it is necessary to fix the anode electrode on the submount before wire bonding on the cathode electrode. - In the case where the cathode electrode is formed in the
groove 20, there is a risk of a short circuit between the anode electrode and the cathode electrode. According to the first embodiment of the present invention, however, the problem of a short circuit between theanode electrode 26 and thecathode electrode 28 can be avoided since thegroove 20 exists between these electrodes. - The
light receiving element 10 according to the first embodiment of the present invention can be variously modified. For example, the outer circumference of the low-reflection film 32 (the opening of the metal mask 30) may be set larger than the inner circumference of thegroove 20 since only light entering the region surrounded by thegroove 20 contributes to the detected current. Thus, the entire pn junction can be used for current generation. Further, the entire lower surface of thesubstrate 12 may be used as a light receiving surface by omitting themetal mask 30. Thus, the amount of light blocked by themetal mask 30 can be reduced by increasing the opening of themetal mask 30 or omitting themetal mask 30, resulting in reduction of the light-electricity conversion loss. - While the first conduction type and the second conduction type are assumed to be the n-type and the p-type, respectively, the conduction types may be reversed. A buffer layer and the like may be provided between the layers. These modifications can be applied as desired to light receiving elements according to embodiments described below. The light receiving elements according to the embodiments described below have a number of commonalities with the first embodiment and will therefore be described mainly with respect to points of difference from the first embodiment.
-
FIG. 3 is a sectional view of a light receiving element according to a second embodiment of the present invention. A portion of the lower surface of thesubstrate 12 is covered with anepitaxial layer 60. The material of theepitaxial layer 60 is not particularly limited as long as it is capable of absorbing light. However, the material of theepitaxial layer 60 is, for example, n-type InGaAs. Theepitaxial layer 60 has an opening right below thediffusion layer 16. A low-reflection film 62 is formed in this opening. - The
metal mask 30 in the first embodiment reflects light and there is a possibility of the reflected light interfering with the incident light. However, in the second embodiment of the present invention, such reflection of light can be prevented since theepitaxial layer 60 capable of absorbing light is formed. -
FIG. 4 is a sectional view of a light receiving element according to a third embodiment of the present invention. This light receiving element is provided with an ion-implantedportion 70 formed, for example, by implantation with Ti and the like. The ion-implantedportion 70 surrounds the boundary between thediffusion layer 16 and thewindow layer 18 as viewed in plan, and extends through thewindow layer 18 and thelight absorbing layer 14 as viewed in section. When light enters the ion-implantedportion 70, no carriers are generated. Also, the ion-implantedportion 70 shuts off the flow of carriers.FIG. 5 is a plan view of the light receiving element shown inFIG. 4 . The ion-implantedportion 70 indicated by a broken line surrounds theboundary 23 between the diffusion layer and the window layer as viewed in plan. - The ion-implanted
portion 70 has the same function as that of thegroove 20 in the first embodiment. In addition, the ion-implantedportion 70, can easily be made by only performing ion implantation after thewindow layer 18 is formed. A suitable combination of the features of the light receiving elements according to the embodiments described above may be made and used. - According to the present invention, the anode electrode and the cathode electrode are formed on the upper surface side of the substrate and a groove or an ion-implanted portion is formed between the anode electrode and the cathode electrode, thereby enabling increasing the response speed and preventing a short circuit between the anode electrode and the cathode electrode.
- Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
Claims (5)
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US10553742B2 (en) | 2016-10-28 | 2020-02-04 | Mitsubishi Electric Corporation | Back-surface-incident type light-receiving device and optical module |
JP6988103B2 (en) * | 2017-02-27 | 2022-01-05 | 三菱電機株式会社 | Manufacturing method of semiconductor devices, semiconductor devices |
US20230215895A1 (en) * | 2020-06-24 | 2023-07-06 | Kyoto Semiconductor Co., Ltd. | Optical semiconductor array |
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JP3008571B2 (en) * | 1991-07-26 | 2000-02-14 | 住友電気工業株式会社 | Light receiving device |
JPH05136447A (en) * | 1991-11-14 | 1993-06-01 | Mitsubishi Electric Corp | Semiconductor photodetector |
JP3419312B2 (en) | 1998-07-21 | 2003-06-23 | 住友電気工業株式会社 | Light receiving element and light receiving element module |
US6043550A (en) | 1997-09-03 | 2000-03-28 | Sumitomo Electric Industries, Ltd. | Photodiode and photodiode module |
JP2001244445A (en) * | 2000-02-28 | 2001-09-07 | Fujitsu Ltd | Optical semiconductor device and manufacturing method thereof |
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JP2005251890A (en) * | 2004-03-03 | 2005-09-15 | Sumitomo Electric Ind Ltd | Upper surface incident light receiving element array |
US7535033B2 (en) * | 2004-09-14 | 2009-05-19 | Banpil Photonics, Inc. | Multicolor photodiode array and method of manufacturing |
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US20070238035A1 (en) * | 2006-04-07 | 2007-10-11 | Micron Technology, Inc. | Method and apparatus defining a color filter array for an image sensor |
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JP2010147158A (en) | 2008-12-17 | 2010-07-01 | Mitsubishi Electric Corp | Semiconductor light-receiving element and method of manufacturing the same |
JP2010045417A (en) | 2009-11-27 | 2010-02-25 | Mitsubishi Electric Corp | Semiconductor photodetector |
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