GB2417825A - LED with a colour purifying diffraction lattice - Google Patents
LED with a colour purifying diffraction lattice Download PDFInfo
- Publication number
- GB2417825A GB2417825A GB0419678A GB0419678A GB2417825A GB 2417825 A GB2417825 A GB 2417825A GB 0419678 A GB0419678 A GB 0419678A GB 0419678 A GB0419678 A GB 0419678A GB 2417825 A GB2417825 A GB 2417825A
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- Prior art keywords
- cpdl
- led
- led structure
- emitting diode
- light emitting
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- 239000000758 substrate Substances 0.000 claims abstract description 17
- 229910052594 sapphire Inorganic materials 0.000 claims abstract 2
- 239000010980 sapphire Substances 0.000 claims abstract 2
- 230000003647 oxidation Effects 0.000 claims description 8
- 238000007254 oxidation reaction Methods 0.000 claims description 8
- 238000005530 etching Methods 0.000 claims description 5
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 4
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims description 3
- 238000001312 dry etching Methods 0.000 claims 3
- 230000001902 propagating effect Effects 0.000 abstract description 21
- 238000001228 spectrum Methods 0.000 abstract description 18
- 238000001914 filtration Methods 0.000 description 11
- 235000012431 wafers Nutrition 0.000 description 10
- 229910002601 GaN Inorganic materials 0.000 description 8
- 238000000605 extraction Methods 0.000 description 8
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 5
- 229910052593 corundum Inorganic materials 0.000 description 5
- 229910001845 yogo sapphire Inorganic materials 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 238000000149 argon plasma sintering Methods 0.000 description 2
- 230000001427 coherent effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/44—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
- H01L33/46—Reflective coating, e.g. dielectric Bragg reflector
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
- H01L2933/0083—Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Led Devices (AREA)
Abstract
A diffraction lattice comprising an array of hexagonal islands formed either on the surface of the LED or at the interface between the LED and a transparent sapphire substrate. The period of the lattice is equal to m g /n where m is an integer, g is the wavelength and n is the refractive index. The height of the islands is equal to g (21+1)/2n where 1 is an integer. The diffractive lattice converts laterally propagating light into vertically emitting light where the spectrum of the emitted light is also filtered.
Description
24 1 7825 TITLE: LIGHT EMIIG DIODE WITH DIFFRACTION LATTICE
BACKGROUND Oli THE INVENTION
1.Field of the Invention
The present invention relates to a method for fabricating a light emitting diodes (LED). More particularly, the invention relates to a method of fabricating LED with pure colour and enhanced light extraction efficiency.
2. Description of the Prior Art
Generally light extraction efficiency of LEDs is limited by high refractive index of the LED chip material which prevents the light escape from the LED chip when its incident angles is higher than the angle of total internal reflection Fig.1. This results in low light extraction efficiency of ordinary LEDs which is typically less than 10%.
To enhance the light extraction efficiency various methods had been proposed.
These are pyramidal-like shaped LED chip taught by M.R.Krames et. al. Applied Physics Letters, 75, pp. 2365, (1999), a random surface texture taught by Schnitzer, et al in Applied Physics Letters 63, 2174 (1993), an ordered interface texturing taught by M.R Krames et al. US 5,779,924.
All above methods allow to suppress the light reflection at the surface of the LED chip and change the angular bandwidth of light which may transmit power into the ambient, but they are not very sensitive to the emitted wavelength.
This does not allow a precise fitting the light extraction properties to a given wavelength and filtering of the light spectrum emitted by the LED.
The present invention allows to overcome this disadvantage by the using of special hexagonal diffraction lattice with precisely determined parameters that allow to convert the laterally propagating light into the vertically propagating light and simultaneously filter the light spectrum emitted by the LED.
SUMMARY OF THE INVENTION
This invention states LED with a colour purifying diffraction lattice (CPDL).
The essence of the invention is in the use of the coherent scattering of the light by the CPDL for colour purifying of the light emitted by the LED and enhancement its extraction efficiency.
Use of CPDL allows to convert the laterally propagating light into the vertically propagating light with high efficiency and, simultaneously filter the light spectrum emitted by the LED.
The LED spectrum filtering by the diffraction lattice allows to purify the colour of the light emitted by LED.Also, the LED spectrum filtering allows to reduce the difference in the wavelengths of the LED chips produced from different part of the wafer and from different wafers.
A method of obtaining the two-dimensional CPDL as a self organized ordered porous pattern of Al2O3 amorphous films developed on Al film by an anodic oxidation. The period and depth of the pores in Al2O3 films are controlled by applied voltage, content of electrolyte and time of oxidation.
BRIEF DES(;RIPTION OF THE DRAWINGS In the accompanying drawings: Fig. l. is a diagram exhibiting the conventional LED without CPDL. Light beam with incident angle higher than the angle of total internal reflection is captured in the chip.
Fig.2. is a principal scheme of the LED chip with CPDL on top surface.
CPDL converts the laterally propagating light into the vertically propagating light.
Fig.3. is a principal scheme of the LED chip with CPDL on interface between LED structure and substrate. CPDL converts the laterally propagating light into the vertically propagating light.
Fig.4. shows first variant of CPDL, d is the period of CPDL, s is the length of the side of hexagon islands forming CPDL.
Fig.5. shows second variant of CPDL, d is the period of CPDL, s is the length of the side of hexagon islands forming CPDL.
Fig.6. shows third variant of CPDL, d is the period of CPDL, r is the radius of the cylindrical holes forming CPDL.
DETAILED DESCRIPTION OF THE PREFERED EMBODIMENTS
The invention will be more fully understood by reference to the following
examples:
EXAMPLE 1
The principal scheme of the LED embodied in Example l is shown in Fig.2. It has a sapphire (Al2O3) substrate l upon which a gallium-nitride-based LED structure 2 is grown.
On the gallium-nitride-based LED structure a two-dimensional CPDL 3 is formed by dry surface etching. The light scattering by CPDL convert the laterally propagating light 4 into the vertically propagating light 5 and, thus, enhance the light extraction efficiency.
S The CPDL structure is shown in Fig.4.
The period d of the CPDL should satisfy the equation d = m}/n, where m=l, 2, 3... and al is the wavelength of the light generated by LED, and n is the refraction index of GaN. To make the scattering with m=l, 2, 3... most effective the zero order of diffraction with m=0 should be suppressed. This happens when height of the hexagonal islands forming CPDL is h = )(21+1)/2n, l=O, l, 2, 3..., and total areas of islands and trenches in CPDL are equal. To make these areas equal the side s hexagon islands should satisfy the equation s = d/22. Thus, for LED with al = 0. 42 1lm the parameters of the CPDL with m = l, 1=0 are d = 0.17 m, h =0.085 m, s = 0.06,um. Use of CPDL allows to convert the laterally propagating light into the vertically propagating light with high efficiency and, simultaneously filter of the light spectrum emitted by the LED.
The LED spectrum filtering by the diffraction lattice allows to purify the colour of the light emitted by LED. Also, the LED spectrum filtering allows to reduce the difference in the wavelengths of the LED chips produced from different part of the wafer and from different wafers.
EXAMPLE 2
The principal scheme of the LED embodied in Example 2 is shown in Fig.3. It has a sapphire (Al2O3) substrate l on which a two-dimensional CPDL 3 is formed by surface etching. On the CPDL a gallium-nitride-based LED structure 2 IS grown.
The CPDL structure is shown in Fig.5.
The light scattering by CPDL convert the laterally propagating light 4 into the vertically propagating light 5 and, thus, enhance the light extraction efficiency.
The period d of the CPDL should satisfy the equation d = m)/n, where m=1, 2, 3... and '1 is the wavelength of the light generated by LED, and n is the refraction index of GaN. To make the scattering with m=1, 2, 3... most effective the zero order of diffraction with m=0 should be suppressed. This happens when heights of the hexagonal islands forming CPDLis h = ;(21+1)/2n, 1=0, 1, 2, 3. . ., and total areas of islands and trenches in CPDL are equal. To make these areas equal the side s hexagon islands should satisfy the equation s = d/22 For LED with = 0.5,um the parameters of the CPDL with m = 2, 1=0 are d= 0.4 Am, h =0.1 sum, s = 0.14 1lm.
Use of CPDL allows to convert the laterally propagating light into the vertically propagating light with high efficiency and, simultaneously filter of the light spectrum emitted by the LED.
The LED spectrum filtering by the diffraction lattice allows to purify the colour of the light emitted by LED.Also, the LED spectrum filtering allows to reduce the difference in the wavelengths of the LED chips produced from different part of the wafer and from different wafers.
EXAMPLES
The principal scheme of the LED embodied in Example 3 is shown in Fig.2. It has a sapphire (Al2O3) substrate 1 upon which a gallium-nitride-based LED structure 2 is grown.
On the gallium-nitride-based LED structure a two-dimensional Al2O3 CPDL 3 is deposited.
The Al2O3 CPDL 3 is formed by an anodic oxidation of Al film.
The CPDL structure is shown in Fig.6.
The period d of the CPDL should satisfy the equation d = m)/n, where m=l, 2, 3... and is the wavelength of the light generated by LED, and n is the refraction index of GaN. To make the scattering with m=1, 2, 3 most effective the zero order of diffraction with m=0 should be suppressed. This happens when depths of the cylindrical holes forming CPDL is h = ) (21+1)/2n, 1 is a positive integer number or zero, and their radii r satisfy the equation r = d(3/4'r)n.
For LED with = 0.5,um the parameters of the CPDL with m = 1, 1=0 are d = 0.21,um, h =0.1 m, r= 0.08 ram.
Use of CPDL allows to convert the laterally propagating light into the vertically propagating light with high efficiency and, simultaneously filter of the light spectrum emitted by the LED.
The LED spectrum filtering by the diffraction lattice allows to purify the colour of the light emitted by LED. Also, the LED spectrum filtering allows to reduce the difference in the wavelengths of the LED chips produced from different part of the wafer and from different wafers.
EXAMPLE 4
The principal scheme of the LED embodied in Example 4 is shown in Fig.2. It has a GaAs substrate l upon which a AlGaInP-based LED structure 2 is grown.
5On the AlGaInP-based LED structure a two-dimensional A12O3 CPDL 3 is deposited.
The Al2O3 CPDL 3 is formed by an anodic oxidation of Al film.
The CPDL structure is shown in Fig.6.
The period d of the CPDL should satisfy the equation d = man, where m=1, 2, 3 and is the wavelength of the light generated by LED, and n is the refraction index of AlGaInP. To make the scattering with m=1, 2, 3... most effective the zero order of diffraction with m=0 should be suppressed. This happens when depths of the cylindrical holes forming CPDL is h = )(21+1)/2n, and l is a positive integer number or zero, and their radii r satisfy the equation r = d(43/4,T)/2.
For LED with = 0.6 Em the parameters of the CPDL with m = 1 are d = O. 18 m, h =0.09 1lm (I = I 0), r = 0.066,um.
Use of CPDL allows to convert the laterally propagating light into the vertically propagating light with high efficiency and, simultaneously filter of the 20light spectrum emitted by the LED.
The LED spectrum filtering by the diffraction lattice allows to purify the colour of the light emitted by LED. Also, the LED spectrum filtering allows to reduce the difference in the wavelengths of the LED chips produced from different part of the wafer and from different wafers.
Many changes and modifications in the above-described embodiments of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.
Claims (17)
- What is claimed is: l. A light emitting diode comprising: a substrate, aLED structure formed on the surface of said substrate; and a twodimensional colour purifying diffraction lattice (CPDL) formed on the surface of said LED structure.
- 2. A light emitting diode as recited in claim l, wherein said substrate is selected from a group consisting of sapphire (Al2O3) and GaAs.
- 3. A light emitting diode as recited in claim l, wherein said LED structure is selected from a group consisting of GaN based and AlGaInP.
- 4. A light emitting diode as recited in claim l, wherein said two dimensional CPDL formed by dry surface etching on the surface of LED structure, the period d of the CPDL satisfy the equation d = man, where m is a positive integer number, is the wavelength of the light generated by LED, and n is the refraction index of LED structure.
- 5. A light emitting diode as recited in claim 1, wherein said two dimensional CPDL formed by an anodic oxidation of Al film and attached to the surface of a LED structure, the period d of the CPDL satisfy the equation d = man, where m is a positive integer number, al is the wavelength of the light generated by LED, and n is the refraction index of LED structure.
- 6. A light emitting diode as recited in claim 1, wherein said two dimensional CPDL formed by dry surface etching on the surface of LED structure and having patterns shown in Fig.4, the period d of the CPDL satisfy the equation d = mean, where m is a positive integer number, is the wavelength of the light generated by LED, and n is the refraction index of LED structure, the height of the hexagonal islands forming CPDLis h = )(21+1)/2n, 1 is a positive integer number or zero, and their side s satisfy the equation s = d/22.
- 7. A light emitting diode as recited in claim l, wherein said two dimensional CPDL formed by dry surface etching on the surface of LED structure and having patterns shown in Fig.5, the period d of the CPDL satisfy the equation d = m)/n, where m is a positive integer number, is the wavelength of the light generated by LED, and n is the refraction index of LED structure, the height of the hexagonal islands forming CPDLis h = )(21+1)/2n, 1 is a positive integer number or zero, and their side s satisfy the equation s = d/242.
- 8. A light emitting diode as recited in claim 1, wherein said two dimensional CPDL formed by an anodic oxidation of Al film attached to the surface of a LED structure and having patterns shown in Fig.6, the period d of the CPDL satisfy the equation d = mean, where m is a positive integer number, is the wavelength of the light generated by LED, and n is the refraction index of LED structure, the depth of the cylindrical holes forming CPDLis h = ;(21+1)/2n, I is a positive integer number or zero, and their radius r satisfy the equation r = d(43/4)"2.
- 9. A light emitting diode comprising: a substrate; a two-dimensional colour purifing diffraction lattice (CPDL) formed on the surface of said substrate; and a LED structure formed on the surface of said CPDL.
- 10. A light emitting diode as recited in claim 9, wherein said substrate is selected from a group consisting of sapphire (A12O3) and GaAs.
- 11. A light emitting diode as recited in claim 9, wherein said LED structure is selected from a group consisting of GaN based and AlGaInP.
- 12. A light emitting diode as recited in claim 9, wherein said twodimensional CPDL formed by dry etching on the surface of substrate upon which a LED structure is grown, the period d of the CPDL satisfy the equation d = man, where m is a positive integer number, al is the wavelength of the light generated by LED, and n is the refraction index of LED structure.
- 13. A light emitting diode as recited in claim 9, wherein said twodimensional CPDL formed by an anodic oxidation of Al film formed on or attached to the surface of substrate upon which a LED structure is grown, the period d of the CPDL satisfy the equation d = man, where m is a positive integer number, al is the wavelength of the light generated by LED, and n is the refraction index of LED structure.
- 14. A light emitting diode as recited in claim 9, wherein said twodimensional CPDL formed by dry etching of substrate upon which a LED structure is grown and having patterns shown in Fig.4, the period d of the CPDL satisfy the equation d = man, where m is a positive integer number, al is the wavelength of the light generated by LED, and n is the refraction index of LED structure, the sleight of the hexagonal islands forming CPDLis h = )/2n, and their side s satisfy the equation * = d/242.
- 15. A light emitting diode as recited in claim 9, wherein said twodimensional CPDL formed by dry etching of substrate upon which a LED structure is grown and having patterns shown in Fig.5, the period the period d of the CPDL satisfy the equation d = main, where m is a positive integer number, is the wavelength of the light generated by LED, and n is the refraction index of LED structure, the height of the hexagonal islands forming CPDL is h = (21+1)/2n, 1 is a positive integer number or zero, and their side s satisfy the equation s = d/212.
- 1 6.A light emitting diode as recited in claim 9, wherein said twodimensional CPDL formed by an anodic oxidation of Al film formed or attached to the surface of substrate upon which a LED structure is grown and having patterns shown in Fig.6, the period d of the CPDL satisfy the equation d = ml/e, where m is a positive integer number, al is the wavelength of the light generated by LED, and n is the refraction index of LED structure, the depth of the cylindrical holes forming CPDL is h = ; (21+1)/2n, 1 is a positive integer number or zero, and their radius r satisfy the equation r = d(>l3/4'T)''2.
- 17. A light emitting diode substantially as herein described with reference to and as illustrated in any of the accompanying drawings.1B. A light emitting diode substantially as herein described with reference to and as specified in any of the examples. ]2
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0419678A GB2417825B (en) | 2004-09-04 | 2004-09-04 | Light emitting diode with diffraction lattice |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0419678A GB2417825B (en) | 2004-09-04 | 2004-09-04 | Light emitting diode with diffraction lattice |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB0419678D0 GB0419678D0 (en) | 2004-10-06 |
| GB2417825A true GB2417825A (en) | 2006-03-08 |
| GB2417825B GB2417825B (en) | 2006-11-22 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0419678A Expired - Fee Related GB2417825B (en) | 2004-09-04 | 2004-09-04 | Light emitting diode with diffraction lattice |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2417825B (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001308457A (en) * | 2000-04-24 | 2001-11-02 | Matsushita Electric Ind Co Ltd | Semiconductor face light emitting element |
| WO2002041406A1 (en) * | 2000-11-16 | 2002-05-23 | Emcore Corporation | Microelectronic package having improved light extraction |
| JP2003086835A (en) * | 2001-09-13 | 2003-03-20 | Univ Tohoku | Semiconductor light emitting element and its manufacturing method |
| US20030057444A1 (en) * | 2001-07-24 | 2003-03-27 | Nichia Corporation | Semiconductor light emitting device |
-
2004
- 2004-09-04 GB GB0419678A patent/GB2417825B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001308457A (en) * | 2000-04-24 | 2001-11-02 | Matsushita Electric Ind Co Ltd | Semiconductor face light emitting element |
| WO2002041406A1 (en) * | 2000-11-16 | 2002-05-23 | Emcore Corporation | Microelectronic package having improved light extraction |
| US20030057444A1 (en) * | 2001-07-24 | 2003-03-27 | Nichia Corporation | Semiconductor light emitting device |
| JP2003086835A (en) * | 2001-09-13 | 2003-03-20 | Univ Tohoku | Semiconductor light emitting element and its manufacturing method |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2417825B (en) | 2006-11-22 |
| GB0419678D0 (en) | 2004-10-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20170904 |