Method of fabricating light emitting diodes

{
  "publication_number": "US6165809A",
  "country": "US",
  "kind": "A",
  "title": "Method of fabricating light emitting diodes",
  "abstract": "According to a light emitting diode fabricating method, when a top surface of an n-type GaAs substrate is inclined at an angle θ with respect to a (1 0 0) plane, a front electrode is formed on a surface shaped portion of a current diffusing layer of a thickness of `d`, the surface shaped portion reflecting a shape of a current blocking portion, in a displaced manner by an amount of approximately d/tan θ from in a direction opposite to a direction in which the surface shaped portion has been displaced with respect to the current blocking portion. Thus, the front electrode is formed in a correct position over the current blocking portion.",
  "claims": [
    "1. A light emitting diode fabricating method comprising the steps of: forming a light emitting layer over a top surface of a semiconductor substrate of a first conductivity type, the top surface being inclined at an angle θ (θ>0) with respect to a (1 0 0) plane of the semiconductor substrate, and then forming a current blocking layer of the first conductivity type over the light emitting layer; partially removing the current blocking layer, wherein the current blocking layer that remains includes one or more current blocking portions; forming an Al x Ga y In 1-x-y P (0≦x≦1, 0≦y≦1) current diffusing layer of a second conductivity type to a specified thickness `d` over the remaining current blocking layer and the light emitting layer, wherein the current diffusing layer has one or more shaped portions reflecting a shape of the remaining current blocking layer and the one or more shaped portions are displaced in a first direction with respect to the remaining current blocking layer, the first direction being parallel to a surface of the remaining current blocking layer; and forming a respective electrode on a surface of each of the one or more shaped portions, each respective electrode being displaced relative to the corresponding shaped portion in a second direction opposite to the first direction by 0.5×(d/tan θ) to 1.5×(d/tan θ) in order to compensate for the displacement in the first direction of the corresponding shaped portion.",
    "2. A light emitting diode fabricating method as claimed in claim 1, wherein the step of partially removing the current blocking layer uses a removal pattern having one or more current blocking portion patterns and a first alignment pattern to thereby leave the one or more current blocking portions and a first alignment portion on or above the light emitting layer, the step of forming a respective electrode on a surface of each of the one or more shaped portions uses an electrode forming pattern having one or more electrode patterns and a second alignment pattern, and forms a respective electrode on a surface of each of the one or more shaped portions by aligning the second alignment pattern with a shaped portion of the current diffusing layer that reflects a shape of the first alignment portion, wherein a position of the second alignment pattern relative to the one or more electrode patterns in the electrode forming pattern is displaced in the first direction by 0.5×(d/tan θ) to 1.5×(d/tan θ) from a position of the first alignment pattern relative to the one or more current blocking portion patterns in the removal pattern.",
    "3. A light emitting diode fabricating method as claimed in claim 1, wherein the current blocking layer is removed such that each of the one or more current blocking portions has a dimension in the second direction larger than that of the corresponding electrode by 0.5×(d/tan θ) to 1.5×(d/tan θ), and each respective electrode is formed such that an end in the second direction of the electrode generally coincides with an end in the second direction of the corresponding shaped portion.",
    "4. A light emitting diode fabricating method as claimed in claim 1, wherein: in the step of removing the current blocking layer, a plurality of portions of the current blocking layer are removed at a pitch A in one or the other of the first and second directions; the thickness d of the current blocking layer satisfies a relationship of 0.5×d/tan θ<A(n -1/2)<1.5×d/tan θ (n: a natural number); and the electrodes are formed on portions of the current diffusing layer that reflect the removed portions of the current blocking layer.",
    "5. A light emitting diode fabricating method as claimed in claim 1, wherein the first direction is a direction that is parallel to the surface of the semiconductor substrate and that is rotated by the angle θ with respect to a [0 1 1] vector.",
    "6. A light emitting diode fabricating method as claimed in claim 1, wherein said semiconductor substrate is a GaAs substrate.",
    "7. A light emitting diode fabricating method as claimed in claim 1, wherein said light emitting layer consists of one or more films of Al x Ga y In 1-x-y P (0≦x≦1, 0≦y≦1).",
    "8. A light emitting diode fabricating method as claimed in claim 1, wherein said semiconductor substrate is inclined in a [0 1 1] or [0 1 1] direction with respect to the (1 0 0) plane.",
    "9. A light emitting diode fabricating method as claimed in claim 8, wherein an angle of inclination of the semiconductor substrate with respect to the (1 0 0) plane in the [0 1 1] or [0 1 1] direction is 5 degrees to 25 degrees.",
    "10. A light emitting diode fabricating method as claimed in claim 1, wherein said current diffusing layer is formed of GaP.",
    "11. A method of fabricating a light emitting diode, comprising the steps of: forming a light emitting layer over a top surface of a semiconductor substrate of a first conductivity type, the top surface of said semiconductor substrate being inclined at an angle θ with respect to the (1 0 0) plane of said semiconductor substrate; forming a current blocking layer of the first conductivity type over said light emitting layer; patterning said current blocking layer using a first alignment pattern to provide a plurality of current blocking portions; forming a current diffusing layer of a second conductivity type over said current blocking portions and said light emitting layer, wherein said current diffusing layer comprises shaped portions that each reflects a shape of a corresponding one of said current blocking portions; and forming a respective electrode on a surface of each shaped portion using a second alignment pattern having electrode patterns that are displaced relative to corresponding current blocking patterns of said first alignment pattern in order to compensate for the displacement of said shaped portions relative to said current blocking portions due to a slow growth of said current diffusing layer on the (1 0 0) plane.",
    "12. A method as claimed in claim 11, wherein said current diffusing layer comprises Al x Ga y In 1-x-y P (0≦x≦1, 0≦y≦1).",
    "13. A method as claimed in claim 11, wherein the current diffusing layer is formed to a thickness d and each respective electrode is displaced relative to its corresponding shaped portion by 0.5×(d/tan θ) to 1.5×(d/tan θ).",
    "14. A method as claimed in claim 11, wherein said semiconductor substrate is a GaAs substrate.",
    "15. A method as claimed in claim 11, wherein said light emitting layer comprises one or more layers of Al x Ga y In 1-x-y P (0≦x≦1, 0≦y≦1).",
    "16. A method as claimed in claim 11, wherein said current diffusing layer comprises GaP.",
    "17. A method as claimed in claim 11, wherein an edge of each respective electrode is aligned with a corresponding edge of its corresponding shaped portion.",
    "18. A method of fabricating a light emitting diode, comprising the steps of: forming a light emitting layer over a top surface of a semiconductor substrate of a first conductivity type, the top surface of said semiconductor substrate being inclined at an angle θ with respect to the (1 0 0) plane of said semiconductor substrate; forming a current blocking layer of the first conductivity type over said light emitting layer; forming a first current diffusing layer of a second conductivity type over said current blocking layer; etching said first current diffusing layer and said current blocking layer to form openings, each said opening being larger at an upper portion thereof than at a lower portion thereof; forming a second current diffusing layer that fills in said openings and covers the remaining portions of said first current diffusing layer, said second current diffusing layer including channel traces caused by the openings etched in said first current diffusing layer and said current blocking layer; and forming an electrode on said second current diffusing layer, said electrode comprising first electrode portions arranged in the channel traces in said second current diffusing layer."
  ],
  "description_excerpt": "The present invention relates to a method for fabricating light emitting diodes to be used for display, transmission or the like.\n\nNowadays, light emitting diodes are widely used for optical communications, information display panels and so on. It is important that the light emitting diodes used for these purposes have a high luminance. The luminance, or the efficiency of such a light emitting diode depends on an internal quantum efficiency and an outward emission efficiency. Among these, the outward emission efficiency is largely influenced by the element structure. To improve the outward emission efficiency, a current blocking layer is formed directly below a bonding pad with a view to suppressing an ineffective emitted light that does not go outside due to blockage by the bonding pad or with a view to reducing an emitted light that is totally reflected on a surface of the light emitting diode.\n\nOne of known light emitting diodes designed to suppress the above-mentioned ineffective emitted light has a structure shown in FIG. 15. This light emitting diode is formed by stacking an n- type layer 62, a light emitting layer 63, a p- type layer 64, p-type current diffusing layers 65 and 66, and an electrode 68 on a front surface of an n-type GaAs semiconductor substrate 61, and another electrode 67 on a rear surface of the substrate 61. Further, an n-type current blocking layer 69 is formed in the p-type current diffusing layer 66 directly below the front electrode 68.",
  "cpc": [
    "H10H 20/824",
    "H10H 20/819",
    "H10H 20/8314"
  ],
  "ipc": [
    "H01L 33/14",
    "H01L 33/16",
    "H01L 33/30",
    "H01L 33/38"
  ],
  "assignees": [
    "Sharp Corp"
  ],
  "inventors": [
    "Takahisa Kurahashi"
  ],
  "filing_date": "1999-02-02",
  "publication_date": "2000-12-26",
  "grant_date": "2000-12-26",
  "priority_date": "1998-02-10",
  "application_number": "US-24147699-A",
  "family_id": "12258058",
  "cited_by_count": 15,
  "citations": [
    "US3900863A",
    "EP0423772A2",
    "JPH06177420A",
    "US5506423A",
    "DE4433867A1",
    "JPH07326815A",
    "US5565694A",
    "JPH0974221A"
  ]
}