Light emitting diode of improved current blocking and light extraction structure
First Claim
1. A light emitting diode, comprising:
- a first electrode;
a substrate formed on said first electrode;
a first confining layer of a first conductivity type formed on said substrate;
an active region formed on said first confining layer;
a second confining layer of a second conductivity type formed on said active region;
a window layer of said second conductivity type formed on said second confining layer, said window layer having a hollow portion extending from the top surface of said window layer and extending into said window layer;
a contact layer of said second conductivity type formed on said window layer for making ohmic contact, said contact layer having a hollow portion extending from the top surface of said contact layer to the bottom surface of said contact layer, thereby exposing said hollow portion in said window layer;
an electrically conductive oxide layer having a lower surface and an upper surface formed on said contact layer, said electrically conductive oxide layer being at least partially transparent, said electrically conductive oxide layer having an outer region and an inner current blocking region, said inner current blocking region of said conductive oxide layer extending from said lower surface of said electrically conductive oxide layer through said hollow portion in said contact layer and into said hollow portion in said window layer, electrical resistivity of said electrically conductive oxide layer being less than electrical resistivity of said window layer and said contact layer; and
a second electrode formed on a portion of said upper surface of said electrically conductive oxide layer, said second electrode being approximately aligned with said hollow portion in said contact layer and said hollow portion in said window layer.
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Accused Products
Abstract
Structures for light emitting diodes are disclosed, which include improved current blocking and light extraction structures. The diodes typically include a substrate formed on a first electrode, a first confining layer of a first conductivity type formed on the substrate, an active region formed on the first confining layer, a second confining layer of a second conductivity type formed on the active region, and a window layer of the second conductivity type formed on the second confining layer. A contact layer of the second conductivity type is formed on the window layer for making ohmic contact, a conductive oxide layer is formed on the contact layer, and a second electrode is formed on the conductive oxide layer. The conductive oxide layer typically includes a central portion located below the second top electrode, which extends into the LED structure, typically beyond the contact layer and into the window layer, or even beyond the window layer, such as into the second confining layer. The improved LED structures preferably include a higher resistive or reverse biased pattern, typically built on or within the substrate, approximately below the second electrode, to further assist the current blocking function. The light emitting diodes preferably include one or more holes which are defined in the conductive oxide layer, or within both the conductive oxide layer and the contact layer, to promote the transmission of light from the upper surface of the light emitting diode. A Distributed Bragg Reflector is also preferably provided between the lower substrate and the first confining layer, to reduce light absorption within the substrate, and to promote efficient light extraction from the top of the LED structure.
156 Citations
57 Claims
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1. A light emitting diode, comprising:
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a first electrode;
a substrate formed on said first electrode;
a first confining layer of a first conductivity type formed on said substrate;
an active region formed on said first confining layer;
a second confining layer of a second conductivity type formed on said active region;
a window layer of said second conductivity type formed on said second confining layer, said window layer having a hollow portion extending from the top surface of said window layer and extending into said window layer;
a contact layer of said second conductivity type formed on said window layer for making ohmic contact, said contact layer having a hollow portion extending from the top surface of said contact layer to the bottom surface of said contact layer, thereby exposing said hollow portion in said window layer;
an electrically conductive oxide layer having a lower surface and an upper surface formed on said contact layer, said electrically conductive oxide layer being at least partially transparent, said electrically conductive oxide layer having an outer region and an inner current blocking region, said inner current blocking region of said conductive oxide layer extending from said lower surface of said electrically conductive oxide layer through said hollow portion in said contact layer and into said hollow portion in said window layer, electrical resistivity of said electrically conductive oxide layer being less than electrical resistivity of said window layer and said contact layer; and
a second electrode formed on a portion of said upper surface of said electrically conductive oxide layer, said second electrode being approximately aligned with said hollow portion in said contact layer and said hollow portion in said window layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
at least one hole defined through said outer region of said electrically conductive oxide layer.
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3. The light emitting diode of claim 2, further comprising:
at least one hole defined through said contact layer and approximately aligned with each of said at least one hole defined through said outer region of said electrically conductive oxide layer.
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4. The light emitting diode of claim 1, wherein the upper surface of said substrate includes a blocking region extending from the top surface of said substrate into said substrate, said blocking region approximately aligned with said inner current blocking region of said electrically conductive oxide layer, said blocking region having an electrical resistivity higher than the electrical resistivity of said substrate.
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5. The light emitting diode of claim 4, wherein said blocking region comprises an oxide region.
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6. The light emitting diode of claim 4, wherein said blocking region comprises a nitride region.
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7. The light emitting diode of claim 1, wherein the upper surface of said substrate includes a blocking region extending from the top surface of said substrate into said substrate, said blocking region approximately aligned with said inner current blocking region of said electrically conductive oxide layer, said blocking region comprising a semiconductor of said second conductivity type.
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8. The light emitting diode of claim 1, wherein said inner current blocking region of said electrically conductive oxide layer is larger than said second electrode.
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9. The light emitting diode of claim 1, wherein the lower surface of said first confining layer includes a blocking region extending from said lower surface of said first confining layer into said first confining layer, said blocking region approximately aligned with said inner current blocking region of said electrically conductive oxide layer, said blocking region having an electrical resistivity higher than the electrical resistivity of said substrate.
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10. The light emitting diode of claim 9, wherein said blocking region comprises an oxide region.
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11. The light emitting diode of claim 9, wherein said blocking region comprises a nitride region.
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12. The light emitting diode of claim 1, wherein the lower surface of said first confining layer includes a blocking region extending from said lower surface of said first confining layer into said first confining layer, said blocking region approximately aligned with said inner current blocking region of said electrically conductive oxide layer, said blocking region comprising a semiconductor of said second conductivity type.
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13. The light emitting diode of claim 1, further comprising:
a distributed Bragg reflector layer of said first conductivity type having a plurality of sublayers formed on said substrate and under said first confining layer.
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14. The light emitting diode of claim 13, wherein said distributed Bragg reflector layer comprises AlxGa1−
- xAs, where x varies between 0 and 1.
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15. The light emitting diode of claim 1, wherein said substrate comprises GaAs.
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16. The light emitting diode of claim 1, wherein said first confining layer comprises (AlxGa1−
- x)1−
yInyP, where x may vary from 0.5 to 1, and y is approximately 0.5.
- x)1−
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17. The light emitting diode of claim 1, wherein said active region comprises (AlxGa1−
- x)1−
yInyP, where x may vary from 0 to 0.4, and y is approximately 0.5.
- x)1−
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18. The light emitting diode of claim 1, wherein said second confining layer comprises (AlxGa1−
- x)1−
yInyP, where x may vary from 0.5 to 1, and y is approximately 0.5.
- x)1−
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19. The light emitting diode of claim 1, wherein said active region comprises an (AlxGa1−
- x)1−
yInyP single quantum well structure, where x may vary from 0 to 0.4, and y is approximately 0.5.
- x)1−
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20. The light emitting diode of claim 1, wherein said active region comprises an (AlxGa1−
- x)1−
yInyP multiple quantum well structure, where x may vary from 0 to 0.4, and y is approximately 0.5.
- x)1−
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21. The light emitting diode of claim 1, wherein said active region comprises an (AlxGa1−
- x)1−
yInyP multiple well structure, where x may vary from 0 to 0.4, and y is approximately 0.5.
- x)1−
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22. The light emitting diode of claim 1, wherein said window layer comprises a material chosen from the group consisting of GaP, GaAsP, AlGaAs, InGaP, AlInGaP, CdS, ZnTe, ZnS, and ZnSe.
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23. The light emitting diode of claim 1, wherein said contact layer comprises a material chosen from the group consisting of GaAs, GaAsP, AlGaAs, InGaAs and InAs.
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24. The light emitting diode of claim 1, wherein said electrically conductive oxide layer comprises a material chosen from the group consisting of indium oxide, tin oxide, cadmium oxide, cadmium tin oxide, and indium tin oxide, zinc oxide, and magnesium oxide.
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25. The light emitting diode of claim 1, wherein said first conductivity type is an n-conductivity type, and wherein said second conductivity type is a p-conductivity type.
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26. The light emitting diode of claim 1, wherein said first conductivity type is a p-conductivity type, and wherein said second conductivity type is an n-conductivity type.
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27. A light emitting diode comprising:
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a first electrode;
a substrate formed on said first electrode;
a first confining layer of a first conductivity type formed on said substrate;
an active region formed on said first confining layer;
a second confining layer of a second conductivity type formed on said active region;
a window layer of said second conductivity type formed on said second confining layer, said window layer having a hollow portion extending from the top surface of said window layer and extending to the bottom surface of said window layer;
a contact layer of said second conductivity type formed on said window layer for making ohmic contact, said contact layer having a hollow portion extending from the top surface of said contact layer to the bottom surface of said contact layer, thereby exposing said hollow portion in said window layer;
an electrically conductive oxide layer formed on said contact layer having an outer region, and an inner current blocking region, said inner current blocking region of said electrically conductive oxide layer extending through said hollow portion in said contact layer, and through said hollow portion in said window layer, electrical resistivity of said electrically conductive oxide layer being less than electrical resistivity of said window layer and said contact layer; and
a second electrode formed on a portion of said electrically conductive oxide layer, said second electrode being approximately aligned with said hollow portion in said contact layer and said hollow portion in said window layer. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
at least one hole defined through said outer region of said electrically conductive oxide layer.
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34. The light emitting diode of claim 33, further comprising:
at least one hole defined through said contact layer and approximately aligned with each of said at least one hole defined through said outer region of said electrically conductive oxide layer.
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35. The light emitting diode of claim 27, wherein the upper surface of said substrate includes a blocking region extending from the top surface of said substrate into said substrate, said blocking region approximately aligned with said inner current blocking region of said electrically conductive oxide layer, said blocking region having an electrical resistivity higher than the electrical resistivity of said substrate.
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36. The light emitting diode of claim 35, wherein said blocking region comprises an oxide region.
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37. The light emitting diode of claim 35, wherein said blocking region comprises a nitride region.
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38. The light emitting diode of claim 27, wherein the upper surface of said substrate includes a blocking region extending from the top surface of said substrate into said substrate, said blocking region approximately aligned with said inner current blocking region of said electrically conductive oxide layer, said blocking region comprising an semiconductor of said second conductivity type.
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39. The light emitting diode of claim 27, wherein size of said inner current blocking region of said electrically conductive oxide layer is larger than size of said second electrode.
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40. The light emitting diode of claim 27, wherein the lower surface of said first confining layer includes a blocking region extending from said lower surface of said first confining layer into said first confining layer, said blocking region approximately aligned with said inner current blocking region of said electrically conductive oxide layer, said blocking region having an electrical resistivity higher than the electrical resistivity of said substrate.
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41. The light emitting diode of claim 40, wherein said blocking region comprises an oxide region.
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42. The light emitting diode of claim 40, wherein said blocking region comprises a nitride region.
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43. The light emitting diode of claim 27, wherein the lower surface of said first confining layer includes a blocking region extending from said lower surface of said first confining layer into said first confining layer, said blocking region approximately aligned with said inner region of said electrically conductive oxide layer, said blocking region comprising a semiconductor of said second conductivity type.
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44. The light emitting diode of claim 27, further comprising:
a distributed Bragg reflector layer of said first conductivity type having a plurality of sublayers formed on said substrate and under said first confining layer.
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45. The light emitting diode of claim 44, wherein said distributed Bragg reflector layer comprises AlxGa1−
- xAs, where x varies between 0 and 1.
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46. The light emitting diode of claim 27, wherein said substrate comprises GaAs.
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47. The light emitting diode of claim 27, wherein said first confining layer comprises (AlxGa1−
- x)1−
yInyP, where x may vary from 0.5 to 1, and y is approximately 0.5.
- x)1−
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48. The light emitting diode of claim 27, wherein said active region comprises (AlxGa1−
- x)1−
yInyP, where x may vary from 0 to 0.4, and y is approximately 0.5.
- x)1−
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49. The light emitting diode of claim 27, wherein said second confining layer comprises (AlxGa1−
- x)1−
yInyP, where x may vary from 0.5 to 1, and y is approximately 0.5.
- x)1−
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50. The light emitting diode of claim 27, wherein said active region comprises an (AlxGa1−
- x)1−
yInyP single quantum well structure, where x may vary from 0 to 0.4, and y is approximately 0.5.
- x)1−
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51. The light emitting diode of claim 27, wherein said active region comprises an (AlxGa1−
- x)1−
yInyP multiple quantum well structure, where x may vary from 0 to 0.4, and y is approximately 0.5.
- x)1−
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52. The light emitting diode of claim 27, wherein said active region comprises an (AlxGa1−
- x)1−
yInyP multiple well structure, where x may vary from 0 to 0.4, and y is approximately 0.5.
- x)1−
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53. The light emitting diode of claim 27, wherein said window layer comprises a material chosen from the group consisting of GaP, GaAsP, AlGaAs, InGaP, AlInGaP, CdS, ZnTe, ZnS, and ZnSe.
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54. The light emitting diode of claim 27, wherein said contact layer comprises a material chosen from the group consisting of GaAs, GaAsP, AlGaAs, InGaAs and InAs.
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55. The light emitting diode of claim 27, wherein said electrically conductive oxide layer comprises a material chosen from the group consisting of indium oxide, tin oxide, cadmium oxide, cadmium tin oxide, and indium tin oxide, zinc oxide, and magnesium oxide.
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56. The light emitting diode of claim 27, wherein said first conductivity type is an n-conductivity type, and wherein said second conductivity type is a p-conductivity type.
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57. The light emitting diode of claim 27, wherein said first conductivity type is a p-conductivity type, and wherein said second conductivity type is an n-conductivity type.
Specification