EPITAXY WAVELENGTH CONVERSION ELEMENT, LIGHT-EMITTING SEMICONDUCTOR COMPONENT, AND METHODS FOR PRODUCING THE EPITAXY WAVELENGTH CONVERSION ELEMENT AND THE LIGHT-EMITTING SEMICONDUCTOR COMPONENT

Abstract

An epitaxial wavelength conversion element (100) is specified which comprises a semiconductor layer sequence (1) with an active layer (10) arranged between a first cladding layer (11) and a second cladding layer (12), the active layer being embodied to absorb light in a first wavelength range and to re-emit light in a second wavelength range, which is different from the first wavelength range, wherein the first cladding layer and the active layer are based on a III-V compound semiconductor material system and wherein the second cladding layer is based on a II-VI compound semiconductor material system.

Furthermore, a light-emitting semiconductor device comprising a light-emitting semiconductor chip and an epitaxial wavelength conversion element and methods for manufacturing the epitaxial wavelength conversion element and the light-emitting semiconductor device are specified.

Claims

1. An epitaxial wavelength conversion element, comprising a semiconductor layer sequence having an active layer arranged between a first cladding layer and a second cladding layer and adapted to absorb light in a first wavelength range and to re-emit light in a second wavelength range different from the first wavelength range, wherein the first cladding layer and the active layer are based on a III-V compound semiconductor material system, wherein the second cladding layer is based on a II-VI compound semiconductor material system, and wherein the second cladding layer is directly adjacent to the active layer.

2. The epitaxial wavelength conversion element according to claim 1, wherein the second cladding layer is a window layer completing the semiconductor layer sequence.

3. The epitaxial wavelength conversion element according to claim 1, wherein the first cladding layer has a roughening on a side remote from the active layer.

4. (canceled)

5. The epitaxial wavelength conversion element according to claim 1, wherein a third cladding layer based on a III-V compound semiconductor material system is arranged between the second cladding layer and the active layer.

6. The epitaxial wavelength conversion element according to claim 1, wherein the III-V compound semiconductor material system is a phosphide and/or arsenide compound semiconductor material system.

7. The epitaxial wavelength conversion element according to claim 1, wherein the active layer is based on InAlGaP and the first cladding layer is based on InAlP.

8. The epitaxial wavelength conversion element according to claim 1, wherein the active layer and the first cladding layer are based on AlGaAs.

9. The epitaxial wavelength conversion element according to claim 1, wherein the second cladding layer comprises one or more Group II elements selected from Mg and Zn and one or more Group VI elements selected from S and Se.

10. A method for manufacturing the epitaxial wavelength conversion element of claim 1, the method comprising the steps: A) growing a first cladding layer and above it an active layer on a growth substrate, the first cladding layer and the active layer being based on a III-V compound semiconductor material system, B) growing a second cladding layer on the active layer, the second cladding layer being based on a II-VI compound semiconductor material system, and C) detaching the growth substrate.

11. The method according to claim 10, wherein the second cladding layer is grown as final layer.

12. A light-emitting semiconductor device, comprising a light-emitting semiconductor chip having a light-outcoupling surface, and an epitaxial wavelength conversion element comprising, a semiconductor layer sequence having an active layer arranged between a first cladding layer and a second cladding layer and adapted to absorb light in a first wavelength range and to re-emit light in a second wavelength range different from the first wavelength range, wherein the first cladding layer and the active layer are based on a III-V compound semiconductor material system, wherein the second cladding layer is based on a II-VI compound semiconductor material system, and wherein the epitaxial wavelength conversion element is arranged with the second cladding layer on the light-outcoupling surface.

13. The semiconductor device according to claim 12, wherein a connection layer comprising a dielectric material is arranged between the light-outcoupling surface and the second cladding layer.

14. The semiconductor device according to claim 12, wherein the second cladding layer is arranged directly on the light-outcoupling surface.

15. A method for manufacturing a light-emitting semiconductor device comprising: providing a light-emitting semiconductor chip having a light-outcoupling surface is provided, forming an epitaxial wavelength conversion element by A) growing a first cladding layer and above it an active layer on a growth substrate, the first cladding layer and the active layer being based on a III-V compound semiconductor material system, B) growing a second cladding layer on the active layer, the second cladding layer being based on a II-VI compound semiconductor material system, and C) detaching the growth substrate, and mounting, between process steps B and C, the semiconductor layer sequence of the epitaxial wavelength conversion element with the second cladding layer on the light-outcoupling surface of the light-emitting semiconductor chip.

Description

[0025] Further advantages, advantageous embodiments and further developments are revealed by the embodiments described below in connection with the figures, in which:

[0026] FIGS. 1A to 1C show schematic illustrations of method steps of a method for manufacturing an epitaxial wavelength conversion element according to an embodiment,

[0027] FIGS. 2A and 2B show schematic illustrations of epitaxial wavelength conversion elements according to further embodiments,

[0028] FIGS. 3A to 3C show schematic illustrations of method steps of a method for manufacturing a light-emitting device and an illustrated band diagram according to a further embodiment, and

[0029] FIG. 4 show schematic illustrations of a method step of a method for manufacturing a light-emitting semiconductor device according to a further embodiment.

[0030] In the embodiments and figures, identical, similar or identically acting elements are provided in each case with the same reference numerals. The elements illustrated and their size ratios to one another should not be regarded as being to scale, but rather individual elements, such as for example layers, components, devices and regions, may have been made exaggeratedly large to illustrate them better and/or to aid comprehension.

[0031] FIGS. 1A to 1C show an embodiment of a method for manufacturing an epitaxial wavelength conversion element 100. For this purpose, as shown in FIG. 1A, a growth substrate 2 is provided on which semiconductor layers based on a III-V compound semiconductor material system are epitaxially grown to form a semiconductor layer sequence 1 as shown in FIG. 1B. The process described below can in particular be carried out on a wafer basis. As growth substrate 2, a substrate wafer can be provided on which the semiconductor layer sequence 1 is grown over a large area. A plurality of wavelength conversion elements 100 can be generated by a final singulation.

[0032] In the embodiment shown, the growth substrate 2 is a GaAs substrate that is equally suitable for growing semiconductor layers based on a phosphide and an arsenide compound semiconductor material system. Here and in the following, embodiments are described in which phosphide compound semiconductor materials are used. Alternatively, it can be possible to use corresponding arsenide compound semiconductor materials instead of the described phosphide compound semiconductor materials.

[0033] A first cladding layer 11 and an active layer 10, each based on a phosphide compound semiconductor material system, are grown on the growth substrate 2. The active layer 10 can be embodied as indicated, for example as a multiple quantum well structure. Alternatively, a single quantum well structure, a pn-junction or a double heterostructure are possible. While the active layer 10 in the embodiment shown comprises InAlGaP with a band gap of about 1.9 eV or more, the first cladding layer 11 comprises InAlP with a larger band gap, in particular with a band gap of about 2.36 eV.

[0034] As shown in FIG. 1B, a second cladding layer 12, based on a II-VI compound semiconductor material system, is grown on the active layer 10. The material of the second cladding layer 12 is selected in such a way that the second cladding layer 12, which is grown directly on the active layer 10, has a larger band gap than the active layer 10 and can also be grown on it in a lattice-matched manner. Furthermore, the material of the second cladding layer 12 is adapted to a desired excitation light wavelength with regard to its transmission properties.

[0035] For example, in the case of green excitation light with a wavelength of, for example, 525 nm, the second cladding layer 12 can preferably comprise or be made of ZnSe with a band gap of 2.71 eV or particularly preferably ZnS.sub.0.08Se.sub.0.92 with a band gap of greater than or equal to 2.71 eV. In the case of blue excitation light with a wavelength of 450 nm, for example, the material of the second cladding layer can preferably be ZnMgSSe with a band gap of greater than or equal to 2.9 eV. Alternatively, tension-stressed ZnS.sub.xSe.sub.1-x can be used as material for the second cladding layer.

[0036] In comparison to phosphide compound semiconductor materials, the use of a II-VI compound semiconductor material for the second cladding layer allows larger band gaps and thus higher light transmission and improved confinement of charge carriers. By lattice-matched growth it can be possible to create a defect free interface between III-V and II-VI compound semiconductor materials, thus eliminating the risk of charge carrier recombination at this interface. The second cladding layer 12 is grown as the last layer of the semiconductor layer sequence 1, so that contamination between the different compound semiconductor material systems can be avoided. Thus, the cladding layer 12 forms a window layer which completes the semiconductor layer sequence 1.

[0037] In particular when using a GaAs growth substrate 2 as described above, it can be advantageous if the growth substrate is thinned or preferably completely removed after the semiconductor layer sequence 1 has been produced, as indicated in FIG. 1C, since GaAs can be opaque especially for light that can be generated by an active layer based on a phosphide compound semiconductor material system.

[0038] FIGS. 2A and 2B show further embodiments of epitaxial wavelength conversion elements 100, which can be manufactured according to the method described above. In contrast to the wavelength conversion element 100 of the previous embodiment, the wavelength conversion element of the embodiment in FIG. 2A has a third cladding layer 13 between the active layer 10 and the second cladding layer 12. Like the first cladding layer 11, this one is based on a phosphide compound semiconductor material system and can, in particular, have the same material as the first cladding layer 11. Due to the smaller band gap and the resulting lower transparency of this material compared to the material of the second cladding layer 12, it can be advantageous if the third cladding layer 13 is thin, in particular with a thickness greater than or equal to 5 nm and less than or equal to 100 nm.

[0039] The epitaxial wavelength conversion element 100 of the embodiment of FIG. 2B shows a roughening 14 on the side of the first cladding layer 11 facing away from the active layer 10. This can be particularly advantageous with regard to light outcoupling and comprise structure sizes, for example, in the range of 200 nm to 1 m. The roughening 14 can be produced, for example, as part of the delamination process to remove the growth substrate or subsequently to it.

[0040] In connection with FIGS. 3A to 3C, a method for manufacturing a light-emitting semiconductor device 200 with an epitaxial wavelength conversion element 100 is described. The wavelength conversion element 100 is embodied purely exemplary according to the embodiment in FIGS. 1A to 1C. Alternatively, the wavelength conversion element 100 can also have features of the other embodiments described above.

[0041] To manufacture the light-emitting semiconductor device 200, as shown in FIG. 3A, a previously provided light-emitting semiconductor chip 4 is attached via a connection layer 3 to the second cladding layer 12 of the semiconductor layer sequence 1 grown on the growth substrate 2. In particular, the method step shown in FIG. 3A can be carried out between the method steps shown in FIGS. 1B and 1C, i.e., before the growth substrate is detached 2. The light-emitting semiconductor chip 4, which has a light-outcoupling surface 41, can be any light-emitting diode chip capable of emitting light at a suitable excitation wavelength. In particular, the method step shown can be carried out in a wafer compound. This means that a semiconductor wafer is provided with a large number of regions corresponding to light-emitting semiconductor chips, while the semiconductor layer sequence 1 is also grown over a large area on the growth substrate 2 which is formed as a substrate wafer. By means of the connection layer 3, the second cladding layer 12 is mounted on the light-outcoupling surface 41, so that the growth substrate 2 is arranged on the side of the semiconductor layer sequence 1 facing away from the light-emitting semiconductor chip 4.

[0042] Dielectric organic or inorganic materials are particularly suitable as connection materials for the connection layer 3. For example, a suitable organic connection material can be BCB, while a suitable inorganic connection material can be SiON. Such materials also have a high transparency for the excitation wavelengths to be used.

[0043] As shown in FIG. 3B, the process step described in FIG. 1C, namely the removal of the growth substrate 2, is then carried out so that the first cladding layer 11 forms a outcoupling layer of the wavelength conversion element 100 and thus also of the light-emitting semiconductor device 200. A large number of such light-emitting semiconductor devices can be produced by singulation of the aforementioned wafer compound. The light outcoupling during operation of the light-emitting semiconductor device 200 can take place directly or also by means of a lens (not shown) to the surrounding air.

[0044] FIG. 3C shows a schematic band diagram for the principal positions of the band gaps of the individual layers of the light-emitting semiconductor device 200 shown in FIG. 3B, wherein in FIGS. 3B and 3C the growth direction 91 of the semiconductor layer sequence 1 and the light emission direction 92 during operation of the light-emitting semiconductor device 200 are indicated. Furthermore, both figures show the interfaces B, T of the wavelength conversion element 100, through which the light is injected (B) and coupled out (T) and at which surface charge carrier recombinations can take place. In addition, the individual layers of the light-emitting semiconductor device 200 in FIG. 3B and the band regions in FIG. 3C are marked with the same Roman numerals for improved allocation. Here, in region III, the band gap of the second cladding layer 12 is marked with the solid line, while the dotted line indicates a band gap that would have a cladding layer based on a phosphide compound semiconductor material corresponding to the first cladding layer 11. Due to the larger band gap of the II-VI compound semiconductor material of the second cladding layer, both a higher transparency for the excitation light emitted by the light-emitting semiconductor chip 4 and an improved confinement of charge carrier pairs can be achieved so that the number of electron-hole pairs generated in the active layer 10 during operation can be increased. Thus, the efficiency of the wavelength conversion element 100 can be improved compared to conventional epi converters based exclusively on III-V compound semiconductor materials.

[0045] FIG. 4 shows a method step corresponding to the method step of FIG. 3A according to a further embodiment, in which the second cladding layer 12 is mounted directly on the light-outcoupling surface 41 of the light-emitting semiconductor chip 4 without a connection layer. This can be achieved in particular by a direct wafer bonding process.

[0046] The features and embodiments described in connection with the figures can also be combined with one another according to further embodiments, even if not all such combinations are explicitly described. Furthermore, the embodiments described in connection with the figures alternatively or additionally can have further features according to the description in the general part.

[0047] The invention is not limited by the description based on the embodiments to these embodiments. Rather, the invention includes each new feature and each combination of features, which includes in particular each combination of features in the patent claims, even if this feature or this combination itself is not explicitly explained in the patent claims or embodiments.

REFERENCE LIST

[0048] 1 semiconductor layer sequence [0049] 2 growth substrate [0050] 3 connection layer [0051] 4 light-emitting semiconductor chip [0052] 10 active layer [0053] 11 first cladding layer [0054] 12 second cladding layer [0055] 13 third cladding layer [0056] 14 roughening [0057] 41 light-outcoupling surface [0058] 91 growth direction [0059] 92 light emission direction [0060] 100 epitaxial wavelength conversion element [0061] 200 light-emitting semiconductor device