OPTOELECTRONIC SEMICONDUCTOR BODY, ARRANGEMENT OF A PLURALITY OF OPTOELECTRONIC SEMICONDUCTOR BODIES, AND METHOD FOR PRODUCING AN OPTOELECTRONIC SEMICONDUCTOR BODY

Abstract

An optoelectronic semiconductor body (10) is provided with a layer stack (11) with an active region (13) which is configured to emit electromagnetic radiation and which comprises a main extension plane, wherein the layer stack (11) comprises side walls (15) which extend transversely to the main extension plane of the active region (13), and the side walls (15) are covered at least in places with a cover layer (16) which is formed with at least one semiconductor material. In addition, an arrangement (18) of a plurality of optoelectronic semiconductor bodies (10) and a method for producing an optoelectronic semiconductor body (10) are provided.

Claims

1. An optoelectronic semiconductor body with a layer stack with: an active region, which is configured to emit electromagnetic radiation and which comprises a main extension plane, wherein the layer stack comprises side walls which extend transversely to the main extension plane of the active region, the side walls are covered at least in places with a cover layer which is formed with at least one semiconductor material, and the cover layer comprises a plurality of layers which are arranged above one another and are doped differently.

2. The optoelectronic semiconductor body according to claim 1, in which the layer stack comprises a p-doped region and an n-doped region, wherein the active region (13) is arranged in the stack direction between the p-doped region and the n-doped region.

3. The optoelectronic semiconductor body according to claim 1, in which the cover layer completely covers the active region on the side walls.

4. The optoelectronic semiconductor body according to claim 1, in which at least one of the side walls encloses an angle of 90° or less than 90° with the main extension plane of the active region.

5. The optoelectronic semiconductor body according to claim 1, in which at least one of the side walls encloses an angle greater than 90° with the main extension plane of the active region.

6. The optoelectronic semiconductor body according to claim 1, in which the lattice mismatch between the material of the cover layer and the material of the layer stack is less than 1%.

7. The optoelectronic semiconductor body according to claim 1, in which the band gap of the material of the cover layer is larger than the band gap of the material of the layer stack.

8. The optoelectronic semiconductor body according to claim 1, in which covalent bonds exist between the material of the side walls and the material of the cover layer.

9. The optoelectronic semiconductor body according to claim 1, in which an upper surface of the layer stack is free of the cover layer.

10. The optoelectronic semiconductor body according to claim 1, in which the side walls are free of traces of a separation process.

11. The optoelectronic semiconductor body according to claim 1, in which the optoelectronic semiconductor body is an electrically pumpable emitter.

12. The optoelectronic semiconductor body according to claim 1, in which the optoelectronic semiconductor body is an optically pumpable emitter.

13. The optoelectronic semiconductor body according to claim 1, in which the layer stack is arranged on a substrate and at least one of the side walls encloses an angle greater than 0° and at most 30° with a crystal direction of the substrate in a plane which is parallel to the main extension plane of the active region.

14. An arrangement of a plurality of optoelectronic semiconductor bodies of claim 1, in which the plurality of optoelectronic semiconductor bodies is arranged in a two-dimensional arrangement.

15. A method for producing an optoelectronic semiconductor body comprising: growing a layer stack with an active region which is configured to emit electromagnetic radiation and which comprises a main extension plane, etching the layer stack so that it comprises, at least in the region of the active region, side walls which extend transversely to the main extension plane of the active region, and growing a cover layer at least in places on the side walls of the layer stack, wherein the cover layer is formed with at least one semiconductor material, and the side walls comprise a curved or inhomogeneous or not straight shape.

16. The method according to claim 15, in which the layer stack comprises a p-doped region and an n-doped region, wherein the active region is arranged in the stack direction between the p-doped region and the n-doped region.

17. The method according to claim 15, in which a masking layer is applied to the layer stack prior to etching the layer stack.

18. The method according to claim 15, in which the cover layer is removed from an upper surface of the layer stack.

19. The method according to claim 15, in which the optoelectronic semiconductor body is separated through the cover layer after growing the cover layer.

20. The method according to claim 15, in which the cover layer is grown by means of metalorganic chemical vapor phase epitaxy.

Description

[0049] FIG. 1 shows an exemplary embodiment of the method for producing an optoelectronic semiconductor body.

[0050] FIGS. 2A, 2B, 2C, 2D, 2E, 2F and 2G show a further exemplary embodiment of the method for producing an optoelectronic semiconductor body.

[0051] FIGS. 3A and 3B show an example of the growth of the cover layer.

[0052] FIGS. 4A and 4B show examples of the separation of exemplary embodiments of optoelectronic semiconductor bodies.

[0053] FIGS. 5A, 5B, 5C and 5D show examples of the growth of the cover layer.

[0054] FIGS. 6 and 7 show top views of exemplary embodiments of the layer stack for exemplary embodiments of semiconductor bodies described here.

[0055] Identical, similar or similarly acting elements are marked with the same reference signs in the figures. The figures and the proportions of the elements to each other shown in the figures are not to be regarded as true to scale. Rather, individual elements may be shown in exaggerated size for better representability and/or comprehensibility.

[0056] FIG. 1 shows an exemplary embodiment of the method for producing an optoelectronic semiconductor body 10. In a first step S1, a layer stack 11 is grown. The layer stack 11 can be grown on a substrate 20. The layer stack 11 comprises a p-doped region 12, an active region 13 and an n-doped region 14. The active region 13 comprises a main extension plane and is configured to emit or receive electromagnetic radiation during operation of the optoelectronic semiconductor body 10. The active region 13 is arranged in a stack direction R between the p-doped region 12 and the n-doped region 14. A masking layer 19 is applied to the layer stack 11. The masking layer 19 may comprise a dielectric material such as SiO.sub.2 or SiN. The masking layer 19 is patterned so that a plurality of individual masking regions 21 are arranged on the layer stack 11. Each masking region 21 defines the size of the layer stack 11 in lateral directions for each optoelectronic semiconductor body 10, wherein the lateral directions extend parallel to the main extension plane of the active region 13.

[0057] In a next step S2, the layer stack 11 is etched so that it comprises, at least in the region of the active region 13, side walls 15 which extend transversely to the main extension plane of the active region 13. The layer stack 11 can be dry-chemically etched in this step. This removes the material of the layer stack 11 which is not covered by the masking regions 21. For example, material of the p-doped region 12, the active region 13 and the n-doped region 14 can be removed. Thus, a plurality of layer stacks 11 is formed on the substrate 20. The individual layer stacks 11 are spaced apart from each other. The side walls 15 of the layer stacks 11 extend at least in the region of the active region 13, but not necessarily as far as the substrate 20.

[0058] In a next step S3, the layer stacks 11 are etched wet-chemically. In this optional step, the shape of the layer stacks 11 can be defined more precisely. In addition, the layer stacks 11 are cleaned in the region which was etched. Regions in which defects are formed during etching can be removed.

[0059] In a next step S4, the growth conditions in an metalorganic chemical vapor phase epitaxy process are adjusted in such a way that material transport takes place in the region of the side walls 15. In this process, for example, material can be transported from the region between two layer stacks 11 to the region of the side walls 15. Thus, the side walls 15 are covered at least in places.

[0060] In a next step S5, a cover layer 16 is grown at least in places on the side walls 15 of the layer stack 11. The previous step S4 is optional, but it can improve the growth of the cover layer 16 on the side walls 15. The cover layer 16 is formed with at least one semiconductor material and is grown epitaxially on the side walls 15. The cover layer 16 is grown by means of metalorganic chemical vapor phase epitaxy. It is possible that the cover layer 16 is also grown on an upper surface 17 of the layer stack 11. This may be an undesired parasitic, polycrystalline growth of cover layer 16. The upper surface 17 of layer stack 11 is the side of layer stack 11 facing away from substrate 20.

[0061] In a next step S6, the parasitically grown cover layer 16 is removed from the upper surface 17 of layer stack 11, for example, by etching or polishing.

[0062] In a next step S7, the optoelectronic semiconductor body 10 is separated through the cover layer 16. This step is optional. A plurality of optoelectronic semiconductor bodies 10 is produced by the separation. The optoelectronic semiconductor bodies 10 can be completely separated. It is further possible that the optoelectronic semiconductor bodies 10 are arranged in a two-dimensional arrangement 18 on a carrier.

[0063] FIGS. 2A to 2G show a further exemplary embodiment of the method for producing an optoelectronic semiconductor body 10. FIG. 2A shows a schematic cross-section of the layer stack 11. The layer stack 11 is arranged on the substrate 20. The layer stack 11 comprises the p-doped region 12, the active region 13 and the n-doped region 14. The n-doped region 14 is arranged on the active region 13. However, it is also possible that the p-doped region 12 is arranged on the active region 13. The masking layer 19 is arranged on the n-doped region 14. In this step, the masking layer 19 is patterned so that a plurality of masking regions 21 are arranged on the layer stack 11. The masking regions 21 can be evenly distributed on the layer stack 11.

[0064] FIG. 2B shows that, in a next step, the layer stack 11 is etched dry-chemically. Thus, a plurality of layer stacks 11 is formed, which are arranged spaced apart from each other.

[0065] The layer stacks 11 comprise side walls 15 which extend perpendicularly to the main extension plane of the active region 13. The p-doped region 12, the active region 13 and the n-doped region 14 are exposed in the region of the side walls 15.

[0066] FIG. 2C shows that, in a next step, layer stack 11 is etched wet-chemically. The side walls 15 are etched in such a way that they are inclined, i.e. extend at an angle of less than 90°, to the main extension plane of the active region 13. In the region of the n-doped region 14, the layer stack 11 is undercut under the masking region 21.

[0067] FIG. 2D shows that, in a next step, a material transport is induced in a metalorganic chemical vapor phase epitaxy process. Material from the regions between the layer stacks 11 is transported to the side walls 15. The dotted line shows that, after the material transport, the side walls 15 are covered with material from the regions between the layer stacks 11. The regions between the layer stacks 11 thus comprise a U-shaped profile. Material transport can improve the quality of a subsequently grown cover layer 16.

[0068] FIG. 2E shows that, in a next step, the cover layer 16 is grown. The cover layer 16 is grown on the side walls 15 and completely covers the regions between the layer stacks 11. Thus, the cover layer 16 completely covers the active region 13 on the side walls 15. In addition, cover layer 16 is grown at least in places on the upper surfaces 17 of layer stacks 11. The parasitic growth of cover layer 16 on the upper surfaces 17 may be undesirable. Covalent bonds may exist between the material of the side walls 15 and the material of the cover layer 16. The lattice mismatch between the material the cover layer 16 and the material of layer stack 11 is less than 1%. To avoid charge carriers in the region of the side walls 15, the band gap of the material of the cover layer 16 may be larger than the band gap of the material of layer stack 11.

[0069] FIG. 2F shows that, in a next step, the masking regions 21 with the cover layer 16 grown thereon are removed. The masking regions 21 can be removed by etching, for example.

[0070] FIG. 2G shows that, in an alternative next step, the cover layer 16 is partially removed so that the upper surface 17 is free of the cover layer 16, and the cover layer 16 terminates flush with the layer stacks 11 on the upper surface 17. For this purpose, the cover layer 16 can be planarized. The masking regions 21 can remain on the layer stacks 11.

[0071] FIG. 2G thus shows an arrangement 18 of a plurality of optoelectronic semiconductor bodies 10, in which the plurality of optoelectronic semiconductor bodies 10 is arranged in a two-dimensional arrangement.

[0072] Each of the semiconductor optoelectronic bodies 10 may comprise a rectangular cross-section, wherein the cross-section is located in a plane which is parallel to the main extension plane of the active region 13. In this case, the substrate 20 may be formed with GaAs or GaP and comprise a (100) or a (110) surface. A (110) surface of the substrate 20 is advantageous if the layer stack 11 comprises InGaAlP to avoid a regular arrangement of the semiconductor compound.

[0073] The arrangement of the individual atoms within an InGaAlP compound can influence the band gap. In addition, the method described here is advantageous in avoiding the growth of a cover layer 16 with a (111)A surface.

[0074] It is further possible that each of the optoelectronic semiconductor bodies 10 comprises a hexagonal cross-section. In this case, the substrate 20 can be formed with GaAs or GaP and comprise a (111)B surface.

[0075] FIGS. 3A and 3B show an example of the growth of cover layer 16. FIG. 3A shows a schematic sectional view of three layer stacks 11 with a cover layer 16 arranged between each of them. Each cover layer 16 comprises a convex shape. The shape of the cover layer 16 can be influenced by the amount of material provided to grow the cover layer 16.

[0076] FIG. 3B shows a schematic sectional view of three layer stacks 11 with a cover layer 16 arranged between each of them. In contrast to FIG. 3A, the cover layer 16 comprises a concave shape. In both cases, in FIG. 3A and FIG. 3B, the cover layer 16 also grows parasitically on the upper surface 17.

[0077] FIG. 4A shows the separation of the optoelectronic semiconductor bodies 10 according to an exemplary embodiment. A schematic sectional view through three optoelectronic semiconductor bodies 10 is shown. The three optoelectronic semiconductor bodies 10 are shown as an example and it is possible that a plurality of optoelectronic semiconductor bodies 10 are arranged side by side. A cover layer 16 is arranged between each of the optoelectronic semiconductor bodies 10. The optoelectronic semiconductor bodies 10 are separated through the cover layer 16. In this case, the cover layer 16 protrudes above the layer stack 11 in stack direction R. Since the optoelectronic semiconductor bodies 10 are separated through the cover layer 16, the side walls 15 are free of traces of a separation process.

[0078] FIG. 4B shows the separation of the optoelectronic semiconductor bodies 10 according to another exemplary embodiment. The structure corresponds to the structure in FIG. 4A, with the difference that the cover layer 16 terminates flush with the layer stack 11 on the upper surface 17. The separated optoelectronic semiconductor bodies 10 can be electrically pumpable emitters such as light emitting diodes. It is further possible that the separated optoelectronic semiconductor bodies 10 are optically pumpable emitters such as converters.

[0079] Each of the optoelectronic semiconductor bodies 10 comprises the layer stack 11 with the p-doped region 12, the active region 13 and the n-doped region 14. The active region 13 is arranged in stack direction R between the p-doped region 12 and the n-doped region 14, and the layer stack 11 comprises the side walls 15, which extend transversely to the main extension plane of the active region 13. In addition, the side walls 15 are covered at least in places with the cover layer 16, which is formed with at least one semiconductor material.

[0080] FIGS. 5A, 5B, 5C, and 5D are examples of the growth of the cover layer 16. FIG. 5A shows a schematic sectional view through a layer stack 11 according to an exemplary embodiment. The p-doped region 12 and the n-doped region 14 have been etched more strongly than the active region 13. In this case, the active region 13 can be formed with InGaAlP and the n-doped region 14 and the p-doped region 12 can be formed with InAlP.

[0081] FIG. 5B shows that, in a next step of the method for producing an optoelectronic semiconductor body 10, material transport is induced in the region of the side walls 15. The material transport of, for example, indium and/or gallium in the region of the active region 13 at the side walls 15 is intensified by the curvature of the active region 13 in the region of the side walls 15. Thus, after the material transport in the active region 13, a semiconductor compound remains in the region of the side walls 15 which comprises less indium and/or gallium and thus has a larger band gap. A larger band gap in the region of the side walls 15 is advantageous to reduce or prevent leakage currents.

[0082] FIG. 5C shows a schematic sectional view through a layer stack 11 according to another exemplary embodiment. The active region 13 was etched more strongly than the p-doped region 12 and the n-doped region 14, for example by irradiating the active region 13 during etching with electromagnetic radiation, which is mainly absorbed in the active region 13.

[0083] FIG. 5D shows that, in a next step of the method for producing an optoelectronic semiconductor body 10, the cover layer 16 is grown on the side walls 15. Since the active region 13 has been etched more strongly than other regions of the layer stack 11, the cover layer 16 comprises a greater thickness in the region of the active region 13 than in other regions. Atoms of the cover layer 16 can therefore advantageously bind to unpaired bonds of the active region 13 and recombination currents in the region of the side walls 15 are reduced or avoided.

[0084] FIG. 6 shows top views of exemplary embodiments of layer stack 11. The layer stack 11 of the optoelectronic semiconductor body 10 is arranged on a substrate 20. The substrate 20 comprises a crystal structure. FIG. 6 shows two crystal directions of the substrate 20 in top view, namely the [100] and the [010] direction. In the exemplary embodiment on the left, the layer stacks 11 comprise a square cross-section. The layer stack 11 can be arranged along a crystal direction of the substrate 20 as shown in the upper left corner. In the exemplary embodiment of layer stack 11 shown below, at least one of the side walls 15 of layer stack 11 encloses an angle a greater than 0° and at most 30° with the [100] direction of substrate 20 in a plane parallel to the main extension plane of active region 13. In the exemplary embodiment on the right, the layer stacks 11 comprise a rectangular cross-section. In this case, the layer stack 11 can be arranged along a crystal direction of the substrate 20, as shown in the upper right corner. In the exemplary embodiment of layer stack 11 shown below, at least one of the side walls 15 of layer stack 11 encloses an angle a greater than 0° and at most 30° with the [100] direction of substrate 20 in a plane parallel to the main extension plane of active region 13.

[0085] FIG. 7 shows top views of other exemplary embodiments of layer stack 11. The substrate 20, on which the layer stack 11 is arranged, comprises a hexagonal crystal structure. On the left in FIG. 7, different directions of the crystal structure of substrate 20 are shown in top view. On the right side in FIG. 7, two exemplary embodiments of layer stack 11 are shown, in which layer stack 11 comprises a hexagonal cross-section. In the upper exemplary embodiment, the layer stack 11 is arranged along the crystal directions of the substrate 20. In the lower exemplary embodiment, at least one of the side walls 15 of the layer stack 11 encloses an angle a greater than 0° and at most 30° with the [−211] direction of the substrate 20 in a plane parallel to the main extension plane of the active region 13.

[0086] The features and exemplary embodiments described in conjunction with the figures can be combined with each other according to further exemplary embodiments, even if not all combinations are explicitly described. Furthermore, the exemplary embodiments described in conjunction with the figures may alternatively or additionally comprise further features according to the description in the general part.

[0087] The invention is not limited to the exemplary embodiments by the description thereof. Rather, the invention comprises each new feature as well as each combination of features, which in particular includes each combination of features in the claims, even if this feature or this combination itself is not explicitly disclosed in the claims or exemplary embodiments.

[0088] The priority of the German patent application DE 102018110187.2 is claimed, the disclosure content of which is hereby incorporated by reference.

REFERENCES

[0089] 10: optoelectronic semiconductor body [0090] 11: layer stack [0091] 12: p-doped region [0092] 13: active region [0093] 14: n-doped region [0094] 15: side wall [0095] 16: cover layer [0096] 17: upper surface [0097] 18: arrangement [0098] 19: masking layer [0099] 20: substrate [0100] 21: masking region [0101] R: stack direction [0102] S1, S2, S3, S4, S5, S6, S7: steps