Flat panel solid state light source

• US 6,329,676 B1
• Filed: 03/01/1999
• Issued: 12/11/2001
• Est. Priority Date: 03/01/1999
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Takayama, Toru, Baba, Takaaki
• Primary Examiner(s): Meier, Stephen D.
• Application Number:
  US09/259,607
• Time in Patent Office: 1,016 Days
• Field of Search: 257/95, 257/98, 257/88
• US Class Current: 257/95
• CPC Class Codes: H01L 27/153 in a repetitive configuration, e.g. LED bars
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 33/0062 for devices with an active region comprising only III-V compounds
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials
• CPC Class Codes: H01L 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material

Abstract

A light emitting diode structure capable of use within a flat panel device with small thickness and large area size. In some embodiments, the LED structure is combined with phosphors to generate light of varying chrominance and luminance including white and other visible spectrum light, and may be used to provide either ambient or accent illumination. The flat panel light source comprises a first GaN cladding layer of a first conductance type, a second GaN cladding layer of a second conductance type formed on the first layer and having at least one window region formed on the first cladding layer, an In_xGa_1−xN active layer and a third cladding layer of an opposite conduction type formed on the second cladding layer. One or more phosphor layers for converting light of a first wavelength to light of a second wavelength may be added to provide polychromatic emissions.

Claims

1. A light emitting diode comprising

a substrate,

a first cladding layer of a first conductivity type disposed above a portion of the substrate, the cladding layer having an upper surface,

an active layer having a thickness disposed over at least a portion of the upper surface of the first cladding layer, said thickness being less than 1 μ

m;

a second cladding layer of a second conductivity type disposed over the active layer, the first cladding layer, the active layer and the second cladding layer forming a ridge with a portion of the active layer exposed at a side of the ridge,

a first electrode disposed to connect electrically to the first cladding layer, and

a second electrode disposed to connect electrically to the second cladding layer.

2. A semiconductor structure comprising:

a substrate;

a first conductive layer of a first conductivity type disposed above at least a portion of the substrate;

an active layer disposed over at least a portion of the first conductive layer, said active layer having a thickness of less than 1 μ

m;

a second conductive layer of a second conductivity type disposed over at least a portion of the active layer, wherein the first conductive layer, the active layer and the second conductive layer together form a ridge with respect to the substrate and wherein a portion of the active layer is exposed at a side of the ridge;

a first electrode disposed to connect electrically to the first conductive layer; and

a second electrode disposed to connect electrically to the second conductive layer.

3. The semiconductor device as recited in claim 2, wherein the second electrode is disposed on and substantially covering the second conductive layer.

4. A semiconductor structure comprising:

a conductive substrate;

a first conductive layer of a first conductivity type disposed above at least a portion of the substrate;

an active layer disposed over at least a portion of the first conductive layer, said active layer having a thickness of less than 1 μ

m;

a second conductive layer of a second conductivity type disposed over at least a portion of the active layer, wherein the first conductive layer, the active layer and the second conductive layer together form a ridge with respect to the conductive substrate and wherein a portion of the active layer is exposed at a side of the ridge;

a first electrode disposed to connect electrically to the first conductive substrate; and

a second electrode disposed to connect electrically to the second conductive layer.

5. A light-emitting semiconductor structure comprising

a substrate;

a first conductive layer of a first conductivity type disposed above at least a portion of the substrate;

an active layer disposed over at least a portion of the first conductive layer, said active layer having a thickness of less than 1 μ

m;

a second conductive layer of a second conductivity type disposed over at least a portion of the active layer, wherein the first conductive layer, the active layer and the second conductive layer together form first and second non-intersecting ridges with respect to the substrate and wherein a portion of the active layer is exposed at adjacent sides of the first and second non-intersecting ridges;

a first electrode disposed to connect electrically to the first conductive layer;

and a second electrode disposed to connect electrically to the second conductive layer.

6. The light-emitting semiconductor structure as recited in claim 5, further comprising a phosphor material disposed between the first and second non-intersecting ridges.

7. A light-emitting semiconductor structure comprising

a substrate;

a first conductive layer of a first conductivity type disposed above at least a portion of the substrate;

an active layer disposed over at least a portion of the first conductive layer, said active layer having a thickness of less than 1 μ

m;

a second conductive layer of a second conductivity type disposed over at least a portion of the active layer, wherein the first conductive layer, the active layer and the second conductive layer together form first and second non-intersecting ridges with respect to the substrate, wherein a portion of the active layer is exposed at adjacent sides of the first and second non-intersecting ridges and wherein a first portion of the second conductive layer forming the first non-intersecting ridge is electrically insulated from a second portion of the second conductive layer forming the second non-intersecting ridge;

a first electrode disposed to connect electrically to the first conductive layer;

a second electrode disposed to connect electrically to the first portion of the second conductive layer; and

a third electrode disposed to connect electrically to the second portion of the second conductive layer.

8. A light-emitting semiconductor structure comprising

a substrate;

a first ridge-shaped light-emitting diode (LED) structure formed on the substrate, the first ridge-shaped LED structure comprising

a first portion of a first conductive layer of a first conductivity type,

a first portion of an active layer disposed over at least a portion of the first portion of the first conductive layer, and

a first portion of a second conductive layer of a second conductivity type disposed over at least a portion of the first portion of the active layer,

wherein a first sub-portion of the first portion of the active layer is exposed;

a second ridge-shaped LED structure formed on the substrate, the second ridge-shaped LED structure comprising

a second portion of the first conductive layer,

a second portion of the active layer disposed over at least a portion of the second portion of the second portion of the first conductive layer, and

a second portion of a second conductive layer of a second conductivity type disposed over at least a portion of the second portion of the active layer, wherein a first sub-portion of the second portion of the active layer adjacent to the first ridge-shaped LED structure is exposed; and

a phosphor material disposed between the first and second ridge-shaped LED structures and in contact with the first sub-portions of the first and second portions of the active layer.

9. The light-emitting semiconductor structure as recited in claim 8, wherein

the first and second portions of the second conductive layer are electrically connected, and the light-emitting semiconductor structure further comprises

a first electrode disposed to connect electrically to the first and second portions of the first conductive layer, and

a second electrode disposed to connect electrically to the first and second portions of the second conductive layer.

10. The light-emitting semiconductor structure as recited in claim 8, wherein:

the first and second portions of the second conductive layer are electrically connected,

the substrate is electrically conductive, and the light-emitting semiconductor structure further comprises

a first electrode disposed to connect electrically to the electrically conductive substrate, and

a second electrode disposed to connect electrically to the first and second portions of the second conductive layer.