Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure
Reexamination Certificate
2002-12-20
2004-03-23
Flynn, Nathan J. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
C257S099000, C257S623000, C257S010000, C257S081000
Reexamination Certificate
active
06710374
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a light-emitting semiconductor component including a thin film stack having a front side, a rear side, an active layer formed with a photon-emitting zone therein, and contact points formed on the front side and rear side of the thin film stack for impressing current into the active layer.
Thin film light-emitting diodes are known, for example, from Published European Patent Application EP 0 905 797 A. The thin film principle is in this case based on internal multiple reflections, combined with internal scattering of the light rays. In this case, the designation “thin” relates in functional terms to the optical thickness of the light-emitting diode. Between two scattering reflections, the absorption suffered by a light ray should be as low as possible.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to further reduce the light absorption in generic light-emitting semiconductor components and in this way to increase the external efficiency of the component.
With the foregoing and other objects in view there is provided, in accordance with the invention, a light-emitting semiconductor component including: a thin film stack having a front side and a rear side, the film stack including an active layer formed with a photon-emitting zone; and a plurality of contact points for impressing current into the active layer, the plurality of the contact points formed on the front side and the rear side. The photon-emitting zone is separated physically from the plurality of the contact points.
In accordance with an added feature of the invention, the active layer is formed with interruptions physically separating the photon-emitting zone from the plurality of the contact points.
In accordance with an additional feature of the invention, the film stack is formed with a plurality of cutouts interrupting the active layer in regions above ones of the plurality of the contact points on the rear side.
In accordance with another feature of the invention, the film stack includes a plurality of regions adjoining the plurality of the cutouts; and the plurality of the regions are formed with at least partly oblique flanks for scattering light.
In accordance with a further feature of the invention, the film stack is formed with a cutout interrupting the active layer in a region around one of the plurality of the contact points on the front side.
In accordance with a further added feature of the invention, the film stack includes a region adjoining the cutout; and the region is formed with at least partly oblique flanks for scattering light.
In accordance with a further additional feature of the invention, a sheathing layer electrically connects the photon-emitting zone to the plurality of the contact points.
In accordance with another added feature of the invention, the sheathing layer has a thickness; and a ratio of the distance between the photon-emitting zone and the nearest one of the plurality of the contact points to the thickness of the sheathing layer is between 1 and 20, inclusive, and even more preferably is between 1 and 10, inclusive.
In accordance with another further feature of the invention, the rear side has a total area; and ones of the plurality of the contact points that are on the rear side assume an area of 2% to 25% of the total area of the rear side, and even more preferably assume an area of 5% to 15% of the total area of the rear side.
In accordance with an added feature of the invention, ones of the plurality of the contact points on the rear side are a plurality of mutually spaced apart contact points.
In accordance with an additional feature of the invention, one of the plurality of the contact points is formed on the front side and defines a central middle contact point.
In accordance with another feature of the invention, ones of the plurality of the contact points on the rear side are a plurality of mutually spaced apart contact points; one of the plurality of the contact points is formed on the front side and defines a central middle contact point; and the plurality of the mutually spaced apart contact points on the rear side are configured on a circumference of a circle and are concentrically configured with respect to the middle contact point on the front side.
In accordance with a further feature of the invention, a highly reflective mirror layer is configured on the rear side, except for locations of ones of the plurality of the contact points on the rear side.
In accordance with a further added feature of the invention, there is provided, a first sheathing layer having a roughened front side. The first sheathing layer is formed on the front side of the film stack, at least in the photon-emitting zone.
In accordance with a further additional feature of the invention, there is provided, a second sheathing layer having a roughened rear side. The second sheathing layer is formed on the rear side of the film stack, at least in the photon-emitting zone.
In accordance with another added feature of the invention, the film stack has a thickness between 3 &mgr;m and 50 &mgr;m.
In accordance with another further added feature of the invention, the film stack has a thickness between 5 &mgr;m and 25 &mgr;m.
In accordance with yet an added feature of the invention, the film stack has a layer sequence based on Al
x
Ga
y
In
1−x−y
P, with 0≦x≦1, 0≦y≦1 and x+y≦1.
In accordance with yet an additional feature of the invention, the film stack includes sheathing layers with material originating from the Al
x
Ga
(1−x)
As material system, with 0≦x≦1.
In accordance with yet another feature of the invention, the active layer is configured between the sheathing layers; and the active layer has material that originates from a material system described by a general formula Al
x
Ga
y
In
1−x−y
P, with 0≦x ≦1, 0≦y≦1 and x+y≦1.
In accordance with yet a further feature of the invention, the film stack has a layer sequence based on Al
x
Ga
(1−x)
As with 0≦x ≦1.
In accordance with yet a further added feature of the invention, the film stack has layers defining planes running through the film stack and through the plurality of the contact points.
With the foregoing and other objects in view there is also provided, in accordance with the invention, an infrared-emitting luminescent diode including: a thin film stack having a front side and a rear side, the film stack including an active layer formed with a photon-emitting zone; and a plurality of contact points for impressing current into the active layer. The plurality of the contact points are formed on the front side and the rear side, and the photon-emitting zone is separated physically from the plurality of the contact points.
According to the invention, in a light-emitting semiconductor component of the type mentioned at the beginning, the photon-emitting zone is arranged physically separated from the contact points in the plane of the thin film stack.
The invention is therefore based on the idea of physically separating the electric contact points and the light-producing areas to keep the light produced in the active zone away from the contact points. Since the contact points with their typical reflectivity of only about 30% contribute substantially to the absorption of the radiation propagating in the thin film stack, the intended aim of reducing the overall absorption is achieved as a result.
In a preferred refinement, the photon-emitting zone is separated physically from the contact points by interruptions in the active layer.
In particular, the thin film stack can advantageously have cutouts interrupting the active layer in a region above the rear-side contact points.
Likewise, the thin film stack can advantageously have cutouts interrupting the active layer in a region around the upper side contact points.
As a result of interrupting the active layer, the cutouts have the effect of physically separating the light-producing zone from the contact points of the up
Forde Kemmon R.
Greenberg Laurence A.
Locher Ralph E.
Osram Opto Semiconductors GmbH
Stemer Werner H.
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