High radiance led chip and a method for producing same
View Patent ↗The invention concerns a light-emitting diode chip ( 1 ) comprising a radiation-emitting active region ( 32 ) and a window layer ( 2 ). To increase the luminous efficiency, the cross-sectional area of the radiation-emitting active region ( 32 ) is smaller than the cross-sectional area of the window layer ( 2 ) available for the decoupling of light. The invention is further directed to a method for fabricating a lens structure on the surface of a light-emitting component.
1. Light-emitting diode chip, comprising a radiation-emitting active region of lateral cross-sectional area FL and a radioparent window layer disposed after said radiation-emitting active region in the direction of radiation and having a refractive index n S , and which, for purposes of the decoupling of light, has a lateral cross-sectional area F C and comprises a decoupling surface adjacent a medium having the refractive index n M , characterized in that
the cross-sectional area F L of the radiation-emitting active region is smaller than the cross-sectional area F C of the decoupling surface, in accordance with the relation:
F L ≦( n M /n S ) 2 ·F C
2. The light-emitting diode chip as recited in claim 1 , characterized in that said radiation-emitting active region is defined by limiting the flow of current to the area F L of said radiation-emitting active region.
3. The light-emitting diode chip as recited in claim 1 , characterized in that the thickness H of said window layer is expressed by:
H
<
(
n
S
n
M
)
·
1
2
·
C
,
where C is the lateral cross-sectional length of said window layer and thus of the light exit surface.
4. The light-emitting diode chip as recited in claim 3 , characterized in that the thickness H of said window layer is expressed by:
H =( C−D )·(2·( n M /n S )) −1
where D is the lateral cross-sectional length of the radiation-emitting active region.
5. The light-emitting diode chip as recited in claim 1 , characterized in that said radiation-emitting active region is composed of plural, regularly spaced active subregions, the total area F L of said subregions being given by:
∑
i
F
Li
=
F
L
≤
(
n
m
/
n
s
)
·
F
c
where F Li denotes the areas of the individual subregions.
6. The light-emitting diode chip as recited in claim 5 , characterized in that the thickness H of said window layer is expressed by:
H=p·A
where A is the regular spacing of said individual subregions and p a selectable factor between 0.5 and 5.
7. The light-emitting diode chip as recited in claim 1 , characterized in that an optical device is provided on said window layer in order to focus electromagnetic radiation emitted by said radiation-emitting active region.
8. The light-emitting diode chip as recited in claim 7 characterized in that
said optical device is realized by means of a lens, the center of which lies over the centroid of the radiation-emitting active region, or by means of plural lenses, the center of each of which lies over a centroid of a respectively assigned active light-emitting subregion.
9. The light-emitting diode chip as recited in claim 8 , characterized in that
said lenses are implemented, at least in part, as Fresnel lenses or as spherical lenses.
10. The light-emitting diode chip as recited in claim 1 , characterized in that said area F L of said radiation-emitting active region is defined by limiting the luminosity of an active layer to said area F L of said radiation-emitting active region.
11. The light-emitting diode chip as recited in claim 1 , characterized in that said area F L of said radiation-emitting active region is defined by an insulating layer realized on or at an active layer and composed of a material that is at least partially opaque and/or to a limited extent translucent to the emitted light from the active layer.
12. A light-emitting diode chip as recited in claim 1 , characterized in that said area F L of said radiation-emitting active region is or are defined by an insulating layer that is realized on or at an active layer and between said active layer and a power supply and that minimizes the supply of power or flow of current to and through said active layer in regions outside said light-emitting region.
13. The light-emitting diode chip as recited in claim 12 , characterized in that
said insulating layer is composed of a nonconductive oxide layer deposited on a side of the chip opposite a light exit surface of the chip.
14. The light-emitting diode chip as recited in claim 1 , characterized in that a power supply is realized by means of an electrical contact disposed on, but not fully covering, a light exit surface of the chip.
15. The light-emitting diode chip as recited claim 1 , characterized in that a power supply is realized by means of an electrical contact connected to said window layer and arranged on a side of said window layer facing away from a light exit surface of the chip.
16. The light-emitting diode chip as recited in claim 1 , characterized in that a power supply is realized by means of an electrical contact connected to said active region.
17. The light-emitting diode chip as recited in claim 12 , characterized in that said power supply and/or said insulating layer is reflective of the emitted light.
18. The light-emitting diode chip as recited in claim 1 , characterized in that a reflecting device for the emitted light is realized in or on said window layer or said active region, on the side of said active region facing away from a light exit surface of the chip.
19. The light-emitting diode chip as recited in claim 18 , characterized in that said reflecting device is a Bragg lattice.
20. The light-emitting diode chip as recited in claim 1 , characterized in that said chip is provided, at least in part, with a covering that is transparent to the emitted light.
21. The light-emitting diode chip as recited in claim 1 , characterized in that it is a light-emitting diode (LED).