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 xe2x80x9cthinxe2x80x9d 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.
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 xcexcm and 50 xcexcm.
In accordance with another further added feature of the invention, the film stack has a thickness between 5 xcexcm and 25 xcexcm.
In accordance with yet an added feature of the invention, the film stack has a layer sequence based on AlxGayIn1xe2x88x92xxe2x88x92yP, with 0xe2x89xa6xxe2x89xa61, 0xe2x89xa6yxe2x89xa61 and x+yxe2x89xa61.
In accordance with yet an additional feature of the invention, the film stack includes sheathing layers with material originating from the AlxGa(1xe2x88x92x)As material system, with 0xe2x89xa6xxe2x89xa61.
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 AlxGayIn1xe2x88x92xxe2x88x92yP, with 0xe2x89xa6x xe2x89xa61, 0xe2x89xa6yxe2x89xa61 and x+yxe2x89xa61.
In accordance with yet a further feature of the invention, the film stack has a layer sequence based on AlxGa(1xe2x88x92x)As with 0xe2x89xa6x xe2x89xa61.
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 upper or rear side of the film thin stack.
The regions of the thin film stack that adjoin the cutouts preferably have at least partly oblique flanks to scatter light. As a result, the scattering processes needed for the thin film light-emitting diode are already made possible by the etching process required to produce the cutouts. An additional process step can be dispensed with.
However, the scattering processes can be introduced in another way, in particular by providing a first sheathing layer with a roughened front side formed on the upper side of the thin film stack, at least in the photon-emitting zone. Alternatively or additionally, a second sheathing layer with a roughened rear side can be formed on the rear side of the thin film stack, at least in the photon-emitting zone.
The photon-emitting zone is expediently connected electrically to the contact points via a sheathing layer. This ensures the electrical contact for feeding current into the active layer. At the same time, the propagation of the radiation produced in the photon-emitting zone is low over the comparatively thin sheathing layer.
The ratio of the distance of the photon-emitting zone from the nearest contact point to the thickness of the electrically connected sheathing layer is advantageously between and including 1 and 20, and even more preferably between and including 1 and 10.
In a preferred refinement, the proportion of the contact points applied to the rear side of the thin film stack assumes an area of 2% to 25%, and even more preferably an area of 5% to 15%, of the total area of the rear side.
In this case, the contact points applied to the rear size of the thin film stack can be formed as a plurality of mutually spaced contact points.
The contact points applied to the front side of the thin film stack can in particular be formed by a central middle contact point.
In a particularly preferred refinement, the contact points of the rear side are arranged on the circumference of a circle and are concentrically arranged with respect to a middle contact point of the front side.
The rear side of the thin film stack, with the exception of the area of the contact points, is expediently provided with a highly reflective mirror layer, which for example, consists of a dielectric such as SiN, SiO2 or the like and a metallization such as Au, Ag, Al or the like.
The thin film stack preferably has a thickness between 3 xcexcm and 50 xcexcm, and even more preferably between 5 xcexcm and 25 xcexcm.
In an expedient refinement, the thin film stack has a layer sequence based on AlxGayIn1xe2x88x92xxe2x88x92yP, where 0xe2x89xa6xxe2x89xa61, 0xe2x89xa6yxe2x89xa61 and x+yxe2x89xa61. The material of the sheathing layers in this configuration can alternatively originate from the AlxGa(1xe2x88x92x)As material system. Likewise, the inventive arrangement can also be used for thin film stacks wholly based on the AlxGa(1xe2x88x92x)As material system, such as for infrared-emitting luminescent diodes.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a light-emitting semiconductor component, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.