Light emitting diode

The invention relates to an LED chip with a Semiconductor body having an epitaxially grown semiconductor layer sequence with an active zone and a radiation , wherein the active zone of the operation at LED chips electromagnetic radiation e-mittiert, the at least partially on the radiation coupling is coupled.

Beanspruc This patent application ht the priority of German Patent Application 10351397.3, the disclosure of which hereby is incorporated by reference.

LED chips are usually by means of a encapsulated capsule mass, which, inter alia, an improved coupling out radiation the electromagnetic radiation to the Environment causes. For this, the LED chips often mounted in a housing, electrically conductive contact and subsequently cast with a casting compound, whereby the resulting component as compared with the LED chip is relatively large.

It is also known an LED chip in a Aabstrahlrichtung nachzuordnen a luminescence conversion material. Under a luminescence conversion material is a understand material having components, means where one of the semiconductor layer sequence during operation of the LED chips emitted electromagnetic radiation convertible to a radiation wavelength changed is.

The luminescence conversion material is usually a capsule mass mixed for encapsulating the LED chips. In addition, for example, in WO 01/65613 the Light emitting semiconductor component having a luminescence conversion element described, in which a luminescence conversion material directly on at least one surface of a The semiconductor body is applied. Thus, a non-homogeneous Distribution of the luminescence conversion material due to largely from Sedimentationsbildung in an encapsulant be avoided.

An object of the present invention is a indicate luminescence, the elements already improved radiation coupling and / or conversion comprising of electromagnetic radiation, and thus in particular further miniaturization of luminescence devices permits.

This object is achieved by a LED chip with the Features of patent claim 1. Advantageous embodiments and preferred developments of the LED chip are in the dependent claims 2 to 15 indicated.

According to the invention of the LED chip a radiolucent Covering on which the radiation in an emission direction of the LED chip is followed and the one of the radiation facing first main surface, a the radiation remote second major surface and the first and the second main surface comprises connecting side surfaces. Between the radiation and the cover body is a connecting layer arranged that covering the connects directly to the semiconductor layer sequence and it is fixed to this. In addition, the compound layer comprises at least one conversion layer having a luminescence conversion material.

The LED chip itself advantageously has already Elements for improved coupling out radiation and Radiation conversion on. Compared to conventional conversion devices the dimensions of the LED chip relatively small, since the cover and the connecting layer placed directly on the semiconductor body and are attached. In other words, adjacent the cover free at the link layer at by which it directly is connected to the semiconductor body, and is not by additional outer holding and / or supporting elements such as a Housing fixed relative to the semiconductor body.

With the LED chip according to the invention can be manufacture smaller components which regards the radiation coupling and / or the radiation conversion no significant show differences to conventional devices, but are significantly reduced compared to this. Of course It is also possible to Lumineszenzdidodenchip how to mount conventional chips such as in a housing and / or to encapsulate having a capsule mass. The housing of a associated component has no conversion elements and can have independently of the conversion requirements be optimized. It can, for example, other optical Elements on the device are arranged.

The bonding layer preferably has a thickness of at most 200 .mu.m, particularly preferably of at most 80 microns.

In addition to its function as an element for improved Radiation coupling is the cover particularly preferably designed as a radiation-shaping optical element. Depending on the specific design of the cover body can thus as a further increased radiation release from the LED chip, or a reduction of the divergence from a disengaged from the luminescence radiation be achieved.

The cover is designed for this purpose with advantage as a cover plate, wherein the side surfaces are not at least partially perpendicular to a main plane of the cover plate extend. Such cover can be easily prepared be and processed.

The side faces of the cover are preferably substantially parabolic, hyperbolic or elliptically curved.

In a particular embodiment, the cover body is provided with Advantage as a CPC, CEC or CHC-like optical concentrator formed, a case which, as well as the following Concentrator is meant whose reflective side faces at least partially and / or at least largely the Form of a compound parabolic concentrator (Compound Parabolic Concentrator, CPC), a composite elliptic concentrator (Compound Elliptic Concentrator, CEC) and / or a compound hyperbolic Concentrator (Compound Hyperbolic Concentrator, CHC) has. Here, the first major surface of the cover of the actual concentrator, so that radiation compared, with the customary use of a concentrator for focusing, in the reverse direction through these runs and thus not concentrated, but the covering with reduced Divergence through the second major surface of leaves.

The second major surface of the covering is preferably at least partly in the form of a refractive and / or diffractive curved or structured lens.

Alternatively or additionally, the cover advantageously holographic structures or elements. Thereby can with the LED chip patterns or graphics are projected.

In a further advantageous embodiment of the LED chip at least the side surfaces of the cover body at least partially coated with a layer or layer sequence, preferably provided with a metallic layer for by the LED chip during its operation Emitted radiation is reflective. This can be achieved be that a greater proportion of radiation in a desired emission direction of the LED chip is emitted.

Advantageously, the cover is provided with a luminescence conversion material added. This luminescence conversion material may be other than in the conversion layer.

Appropriately, the covering essentially of formed of a material whose expansion coefficient substantially the expansion coefficient of a material of Semiconductor layer sequence corresponds. Preferably, the cover body a material which consists essentially of a Borosilicate glass or based on a borosilicate glass.

The link layer has advantageously comprises an adhesive, preferably to a silicone-based adhesive. An advantage of a silicone-based adhesive is, that this over a relatively low sensitivity comprises ultraviolet radiation.

Particularly preferably, the LED chip is a thin-film LED chip, of itself through the following characteristics stand out:<ul><li>to a to a carrying member facing the first Major surface of the semiconductor layer sequence is a reflective applied layer, or formed, at least a portion of the generated in the Halöbleiterschichtenfolge electromagnetic radiation in these reflected back;</li><li>the semiconductor layer sequence has a thickness in the range of 20 microns or less, more preferably in the range of 10 microns on; and</li><li>the semiconductor layer sequence contains at least one semiconductor layer with at least one area, the mixing structure a which, in the ideal case to an approximately ergodic distribution of the light in the epitaxial Epitaxial leads, a say that it has ergodic possible stochastic scattering behavior on.</li></ul>

A basic principle of a thin-film LED chips for example in I. Schnitzer et al., Appl. Phys. Lett. 63 (16), 18 Oct. 1993, 2174-2176, the disclosure content this respect is hereby incorporated by reference becomes.

The LED chip is in an alternative embodiment, provided for a flip-chip mounting, which results in has that the radiation output of a semiconductor layer sequence opposite outer surface of a substrate of the semiconductor body. is in a flip-chip the radiation output free of electrical contact material, so that the covering surface over the entire Radiation output may be applied.

Further advantages, preferred embodiments and further developments the LED chip emerge from the in explained below in connection with Figures 1 to 6 Embodiments. Show it:<sl><li>1 shows a first embodiment of an LED chip in a schematic representation;</li><li>2 shows a second embodiment of an LED chip in a schematic representation;</li><li>3 shows a third embodiment of an LED chip in a schematic representation; </li><li>4 shows a fourth embodiment of an LED chip in a schematic representation;</li><li>Figure 5 shows a fifth embodiment of an LED chip in a schematic representation, and</li><li>Figure 6 shows a sixth embodiment of an LED chip in a schematic representation.</li></sl>

are in the exemplary embodiments and figures, identical or like-acting elements each with the same reference numerals provided. The illustrated components and the Size relationships among the constituent parts are not to be regarded as true to scale. Rather, some details the figures for better understanding exaggerated.

The LED chip illustrated in Figure 1 comprises a Semiconductor body 20 comprising a substrate 14 and provided thereon, applied epitaxially grown semiconductor layer sequence 1 comprises. Facing away from the substrate 14 outer face the semiconductor layer sequence 1 is a radiation 2 of the semiconductor body 20. In the radiation 2 is a bonding layer 30 which the compound disposed on the layer 30 covering 6 connects with the semiconductor body 20 and on the semiconductor body 20 attached. The connection layer 30 has in the Embodiments parallel to the radiation output 2 is an expansion on that approximately to the extent of the radiation equivalent.

The substrate 14 may be a growth substrate, which is, that the semiconductor layer sequence 1 directly on the substrate 14 grew up. Alternatively, the substrate 14 can also be a its carrier substrate, such as for example, in thin-film LED chips the case is. In this case, for preparing of the semiconductor body 20, the semiconductor layer sequence 1 initially grown on a growth substrate and subsequently with the major surface facing away from the growth substrate applied to a support substrate. The growth substrate is at least partially from the semiconductor layer sequence 1 away. Further characteristics of thin-film LED chips are generally part of the description called.

Thin-film LED chips have a nearly Lambertian Radiation on what particularly advantageous is when the radiation output 2 with a thin Conversion layer 3 is covered, since almost the entire Radiation through the radiation coupling 2 and only one small portion is coupled laterally.

The semiconductor layer sequence 1 is based for example on a nitride compound semiconductor material, ie at least one layer the semiconductor layer sequence has a material from the system In_xAl_yga_1-xyN on with 0 ≤ x ≤ 1, 0 ≤ y ≤ 1 and x + y ≤ 1st In addition, the semiconductor layer sequence may, for example, a 1 have multi-quantum well structure, such as those described in WO 01/39282 A2 describes the disclosure of which so far is hereby incorporated by reference.

Instead of the multi quantum well structure may also be a single quantum well structure, a double hetero structure or a Single-heterostructure used.

The cover 6 has a first major surface 7, a second Main surface 8 and the first and the second main surface 7, 8 interconnecting side faces 9 on. The first major surface 7 borders on a conversion layer 3 of the link layer 30 at.

In a production of LED chips, for example, the conversion layer 3 on the cover body 6 be applied. The conversion layer is then again eg by means of a silicone-based adhesive 5 on the radiation 2 is applied. The first major surface the cover body is formed expediently smooth and the luminescence conversion material is in a Layer of high uniformity applied. This may of be advantageous if the radiation output roughened eg , whereby a conversion layer is limited to Apply evenly could.

By using a cover body for applying the Conversion layer 3, the application may also be carried out at conditions suitable for a functionality the semiconductor layer sequence may be harmful, such as relatively high pressure and / or relatively high temperatures.

In the LED chip are illustrated in Figure 1 the side faces 9 of the cover 6 and the adjacent Conversion layer 3 having a reflective layer or Layer sequence 12, for example, a metal layer of silver provided. Alternatively, only the side faces 9 of the cover be coated completely or partially. 6

Due to the reflective coating 12 electromagnetic Rays (shown in Figure 1 by the arrow), the laterally without the reflective coating 12 of the cover body would 6 decoupled, reflected back. The bevelled side faces 9 of the cover 6 cause that a large part of the electromagnetic radiation, the result of multiple total internal reflection in the Covering 6 and the conversion layer 3 are held, be reflected such to Strahlungsaufkoppelfläche 8, that they couple out on this from the cover body. 6

The conversion layer 3 has a luminescence conversion material in which, for example of at least one phosphor exist. For this example, suitable inorganic phosphors, as with rare earths (particularly Ce) doped Garnets, or organic phosphors such as perylene phosphors. Further suitable phosphors are, for example, listed in WO 98/12757, the content of which insofar is hereby incorporated by reference.

The luminescence conversion material can in a matrix material be embedded, which, for example, an equal Material seinkann as that made from the the cover 6 is. By the same materials and thus same Refractive indices can reflections of electromagnetic Rays at the interface between the conversion layer 3 and the cover body 6 are largely avoided.

As material for the cover body 6 and / or the matrix material the conversion layer 3 are glasses suitable, for example a Borosilicate glass. The borosilicate glass, because of its precise Composition has a coefficient of thermal expansion have coupled to the expansion coefficient of the is adapted to the semiconductor body 20, ie, that the matrix material the conversion layer 3 have the same or at least similar coefficient of expansion as the layers Semiconductor body 20th

The semiconductor layer sequence 1 has on its surface a electrically conductive contact and a bond pad 10, to which a bonding wire 11 is soldered by means of which the semiconductor layer sequence, 1 from one side to a voltage source may be connected electrically conductive. Of the Bonding wire 11, however, does not belong here for luminescence even.

To the greatest possible continuous surface for applying of the cover 6 on the semiconductor layer sequence 1 release, the bonding pad 10 is at one edge of the radiation 2 is arranged. Alternatively, it is also possible that the cover body 6 and the link layer 30 are provided in the middle with a hole and that the Bond pad 10 located at the center of the radiation 2 is, as is the case in general. As a result, a symmetrical loading of the semiconductor body 20 be achieved with electric current.

Another possibility is, the semiconductor body 20 for a provide flipchip assembly, so that all electrical formed pads on the semiconductor layer sequence, are and the radiation coupling an opposite to the Side-facing surface of a substrate of the semiconductor body 20. With a flip, the radiation output is free of any contact material. A component with a flip-chip is, for example, in WO 01/47039 A1 discloses, the disclosure of which so far is hereby incorporated by reference.

The LED chip shown in the Figures 1 to 5 each differ by their different shaped cover body. 6

The cover 6 of the LED chip shown in Figure 2 includes as well as the cover shown in Figure 1 6 side surfaces 9 which obliquely to a main plane of extension of the cover 6 extend. A difference However, between these cover bodies that in Figure 2 illustrated a second main surface 8 having the not parallel to a main plane of the cover 6 runs, but is lens-like convex. This improves the decoupling of radiation and a reaches more beamforming.

An alternative shaping of the second main surface 8 of the cover body 6 is shown in FIG. 3 The second major surface 8 here has the form of a TIR lens (Total Internal Reflection-lens) on whose structures beamforming cause by total internal reflection.

The cover 6 of the LED chip shown in Figure 4 does not flat, but parabolic Side faces 9. Overall, this covering 6 the shape of a CPC-like optical concentrator on, the in the reverse direction for decreasing the divergence of the used the semiconductor layer sequence 1 emitted radiation becomes.

Again, it is possible, by a particular configuration the second main surface 8 to cause further beam shaping. Thus, the second main surface 8, as shown in Figure 5 be formed lenticular curved outward or as shown in Figure 6 may have a structure that a Beamforming effected by means of total internal reflection.

In Figure 6, the lateral surfaces 9 of the cover 6 also partially curved and partially flat. About that addition, the second main surface 8 of the six shown in Figure Cover body diffractive surface structures 13 on which symbolically represented by the dashed line are. By such diffractive structures, a further Beam shaping and / or improved radiation outcoupling or decreased reflectivity of the second main surface 8 be effected. When the cover 6 as appropriate from a Plastic is made, the diffractive blank create structures such as by hot stamping.

Additionally or alternatively to the design options mentioned above the cover body 6, this also be provided with holographic structures or elements.

In contrast to the LED chips shown in the Figures 1 to 5 has the shown in Figure 6 a second conversion layer 4.

The luminescence conversion material of the second conversion layer 4 may be the same as that of the first conversion layer 3. Bring one in the production of LED chips first the second conversion layer 4 and measures below the color locus of the LED chip, so you can by a specific choice of the amount of luminescence conversion material in the first conversion layer 3 a Fine tuning of the color location of the resulting LED chips carry out. Alternatively, it is also possible that the first and the second conversion layer 3, 4 different luminescence conversion materials, for example, comprise different phosphors.

Additionally or alternatively, can be the cover body 6 itself form of a material with a luminescence conversion material is offset. Thus, the invention provides Procedure as a whole a lot of possibilities to shape the resulting color space of the LED chip.

In the LED chip shown in the figures 1 to 6 is in each case on the first major surface 7 of the cover 6, a conversion layer 3 applied. However, it is also possible only conversion layer on the Strahluingsauskoppelfläche 2 of the semiconductor body 20 apply.

In addition, a conversion layer on the second its main surface 8 of the cover 6 is applied, so that this conversion layer not between the cover body 6 and the semiconductor body 20 but on that of the semiconductor body located 20 opposite side of the cover 6 is. Luminescence conversion materials of different conversion layers may each at least partially identical or be different.

The LED chips are also particularly suitable for the production of car headlights, as in the German Patent Application 10314524.9 describes the disclosure of this respect is hereby incorporated by reference becomes.

The scope of the invention is not by the description the invention based on the embodiments limited. Thus, it is for example possible that the second Conversion layer not only on the radiation coupling of the semiconductor body but also to side faces of this is applied, so that even seiltich from the semiconductor body decoupled electromagnetic radiation in a radiation modified wavelength is converted. moreover it is possible that the transition from the side surfaces the cover body is not clear defined for the second main surface is but rather that the second major surface fluent merges into the side surfaces or directly to the first major surface adjacent.

The invention encompasses any new feature and any combination of features, any combination of features of different Claims and various embodiments includes, even if this combination each is not explicitly specified.