Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With reflector – opaque mask – or optical element integral...
Reexamination Certificate
2000-12-07
2003-06-10
Jackson, Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With reflector, opaque mask, or optical element integral...
C257S099000, C257S100000
Reexamination Certificate
active
06576930
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a light-radiating semiconductor component with a semiconductor body that emits electromagnetic radiation during operation of the semiconductor component. The component has at least one first and at least one second electrical terminal, which are electrically connected to the semiconductor body. The component further has a luminescence conversion element with at least one luminescent material.
A semiconductor component of that type is disclosed, for example, in German published patent application DE 38 04 293. There, an arrangement having an electroluminescent or laser diode in which the entire emission spectrum radiated by the diode is shifted toward greater wavelengths by means of a plastic element that is treated with a fluorescent, light-converting organic dye. The light radiated by the arrangement consequently has a different color from the light emitted by the light-emitting diode. Depending on the nature of the dye added to the plastic, light-emitting diode arrangements which emit light in different colors can be produced using one and the same type of light-emitting diode.
German published patent application DE 23 47 289 discloses an infrared (IR) solid-state lamp in which luminescent material is applied on the edge of an IR diode and converts the IR radiation that is radiated there into visible light. The aim of this measure is, for supervisory purposes, to convert a smallest possible part of the IR radiation emitted by the diode into visible light in conjunction with the smallest possible reduction of the intensity of the emitted IR radiation.
Furthermore, European patent application EP 486 052 discloses a light-emitting diode in which at least one semiconductor photoluminescent layer is arranged between the substrate and an active electroluminescent layer. The semiconductor photoluminescent layer converts the light of a first wavelength range—the light emitted by the active layer in the direction of the substrate—into light of a second wavelength range, with the result that, altogether, the light-emitting diode emits light of different wavelength ranges.
In many potential areas of application for light-emitting diodes, such as, for example, in display elements in motor vehicle dashboards, lighting in aircraft and automobiles, and in full-color LED displays, there is increasingly a demand for light-emitting diode arrangements with which polychromatic light, in particular white light, can be produced.
Japanese patent application JP-07 176 794-A describes a white-light-emitting, planar light source in which two blue-light-emitting diodes are arranged at an end of a transparent plate. The diodes emit light into the transparent plate. The transparent plate is coated with a fluorescent substance on one of the two mutually opposite main surfaces. The fluorescent substance emits light when it is excited by the blue light of the diodes. The light emitted by the fluorescent substance has a different wavelength from that of the blue light emitted by the diodes. In that prior art component, it is particularly difficult to apply the fluorescent substance in such a manner that the light source radiates homogeneous white light. Furthermore, the question of reproducibility in mass production also poses major problems because even slight fluctuations in the thickness of the fluorescent layer, for example on account of unevenness of the surface of the transparent plate, cause a change in the shade of white of the radiated light.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a light-radiating semiconductor component, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which radiates homogeneous polychromatic light and ensures technically simple mass production with component characteristics that are reproducible to the greatest possible extent.
With the foregoing and other objects in view there is provided, in accordance with the invention, a light-radiating semiconductor component, comprising:
a semiconductor body emitting electromagnetic radiation during an operation of the semiconductor component, the semiconductor body having a semiconductor layer sequence suitable for emitting electromagnetic radiation of a first wavelength range selected from a spectral region consisting of ultraviolet, blue, and green;
a first electrical terminal and a second electrical terminal each electrically conductively connected to the semiconductor body; and
a luminescence conversion element with at least one luminescent material, the luminescence conversion element converting a radiation originating in the first wavelength range into radiation of a second wavelength range different from the first wavelength range, such that the semiconductor component emits polychromatic radiation comprising radiation of the first wavelength range and radiation of the second wavelength range.
The invention provides for the radiation-emitting semiconductor body to have a layer sequence, in particular a layer sequence with an active semiconductor layer made of Ga
x
In
1-x
N or Ga
x
Al
1-x
N, which emits an electromagnetic radiation of a first wavelength range from the ultraviolet, blue and/or green spectral region during operation of the semiconductor component. The luminescence conversion element converts part of the radiation originating from the first wavelength range into radiation of a second wavelength range, in such a way that the semiconductor component emits polychromatic radiation, in particular polychromatic light, comprising radiation of the first wavelength range and radiation of the second wavelength range. This means, for example, that the luminescence conversion element spectrally selectively absorbs part of the radiation emitted by the semiconductor body, preferably only over a spectral subregion of the first wavelength range, and emits it in the region of longer wavelength (in the second wavelength range). Preferably, the radiation emitted by the semiconductor body has a relative intensity maximum at a wavelength &lgr;≦520 nm and the wavelength range which is spectrally selectively absorbed by the luminescence conversion element lies outside this intensity maximum.
In accordance with an added feature of the invention, the luminescence conversion element converts radiation of the first wavelength range into radiation of a plurality of second wavelength ranges from mutually different spectral subregions, such that the semiconductor component emits polychromatic radiation comprising radiation of the first wavelength range and radiation of the plurality of second wavelength ranges. In other words, the invention advantageously makes it possible also to convert a number (one or more) of first spectral subregions originating from the first wavelength range into a plurality of second wavelength ranges. As a result, it is possible to produce diverse color mixtures and color temperatures.
The semiconductor component according to the invention has the particular advantage that the wavelength spectrum generated by way of luminescence conversion and hence the color of the radiated light do not depend on the level of the operating current intensity through the semiconductor body. This has great significance particularly when the ambient temperature of the semiconductor component and, consequently, as is known, also the operating current intensity greatly fluctuate. Especially light-emitting diodes having a semiconductor body based on GaN are very sensitive in this respect.
In addition, the semiconductor component according to the invention requires only a single driving voltage and, as a result, also only a single driving circuit configuration, whereby the outlay on devices for the driving circuit of the semiconductor component can be kept very low.
In accordance with an additional feature of the invention, the semiconductor component has a defined main radiating direction, and the luminescence conversion element is disposed substantially
Höhn Klaus
Reeh Ulrike
Schlotter Peter
Schmidt Ralf
Schneider Jürgen
Jackson Jerome
Osram Opto Semiconductors GmbH
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